Copolymerization of carbon dioxide and cyclic monomers to form polycarbonates

ABSTRACT

Embodiments of the present disclosure describe initiating systems comprising an activator and an initiator, wherein the activator includes an alkyl borane or alkyl aluminum, wherein the initiator includes an organic cation and either an alkali metal or a compound containing an active protic hydrogen. Embodiments of the present disclosure further describe methods of making a polycarbonate comprising contacting a cyclic monomer and carbon dioxide in the presence of an activator and an initiator to form a polycarbonate, wherein the catalyst is one or more of an alkyl borane and alkyl aluminum, wherein the initiator includes an organic cation and either an alkali metal or a compound containing an active protic hydrogen.

BACKGROUND

Carbon dioxide (CO₂) is an abundant, inexpensive, and non-toxicrenewable Cl resource for the production of value-added chemicals andmaterials. Chemical fixation of carbon dioxide is an important researchfield of green chemistry. Alternating copolymerization of carbondioxide-based polycarbonate is one of its most important applications.This polymer not only has excellent barrier properties to oxygen andwater, but also has excellent biocompatibility and biodegradability.Polycarbonates can be used as engineering plastics, non-pollutingmaterials, disposable medical and food packaging, adhesives andcomposite materials.

In 1969 Inoue, et al. discovered that CO₂ could be incorporated into thepolymer chain to form polycarbonates through the copolymerization withepoxides. Since then, especially during the past two decades,significant progresses have been made in this area. Generally, thecatalysts used for the copolymerization of CO₂ and epoxide are compoundsbased on transition metals or earth-abundant main group metals such as,Zn, Co, Cr, Mg, Al, which are either insoluble or soluble in thereaction system during copolymerization. The most successful CO₂-epoxidecopolymerization systems are based on transition metal Cr(III), Co(III)or Zn(II) complexes with Schiff base ligands. In the case ofcopolymerization of CO₂ and propylene oxide (PO), totally alternatedpoly(propylene carbonate) (PPC) with molar mass up to 300,000 g mol⁻¹could be prepared using a recyclable catalyst (salen) Co(III) (S.Sujith, et. al, Angew. Chem. Int. Ed., 2008, 47, 7306).

In this context, many patents have been filed for the production ofpolycarbonates or polyol depending on the catalysts used, includingheterogeneous ones represented by zinc glutarate and double metalcyanides (DMCs): U.S. Pat. No. 6,713,599, 6,815,529, 6,844,287,8,093,351, WO2011144523; and homogeneous ones represented by cobalt andchromium with salen ligands: U.S. Pat. No. 7,304,172, US20110207909,WO2009130470. Homogeneous catalysts are of more active and higherselectivity with respect to the heterogeneous ones. However, the formerneed multi-step synthesis due to the complexity of ligands. In addition,whatever catalysts used during copolymerization, the polycarbonatesproduced are contaminated with metals which give color and toxicity. Apost-polymerization removal step is necessary for stability and broadapplicability especially in the commodity area including SacrificialBinder, Electronic Processing, and Packaging.

There are a very large range of commercially available and naturallyoccurring epoxides, the diversities of epoxides could produce thepolycarbonates with different properties. For instance, the Tg values ofproduced polycarbonates from epoxides 1-dodecene oxide, cyclohexeneoxide, 1,4-dihydronaphthalene oxide span from −38, 118, to 150° C.,where the latter is very close to the conventional bisphenol-Apolycarbonate. In addition, terpolymerization of two or more epoxidemonomers can tune the properties of random polycarbonate copolymersproduced. (Darensbourg and Wang 2014; Seong et al. 2010; Ren et al.2010) On the other hand, sequential polymerization of epoxides with CO₂can afford a polycarbonate block copolymer. Darensbourg et al. reportedthe synthesis of ABA triblock polycarbonates through sequential additionof propylene oxide and allyl glycidyl ether, using water as achain-transfer reagent; (Wang, Fan, and Darensbourg 2015) similarly, Tanet al. described the copolymerization of cyclohexene oxide and4-vinyl-1-cyclohexene-1,2-epoxide with CO₂, producing polycarbonateblock copolymer through sequential addition of monomers in one pot. (Hsuand Tan 2002, 2003) The pendant vinyl groups could thus be furtherfunctionalized for other applications. (Darensbourg 2017) Due to theselectivity of catalysts, it should be noted that epoxide monomerschosen for block copolymerization have similar structures, in otherwords, they are either terminal epoxides (propylene oxide) or internalepoxides (cyclohexene oxide).

To improve the thermal and mechanical properties of most investigatedpolycarbonates, (PPC) and poly(cyclohexenecarbonate) (PCHC), or endowdegradable properties to other polymeric materials, incorporation of twoor more other blocks into the polycarbonates to form block copolymers isindispensable. One strategy is the copolymerization of CO₂ with otherepoxides which could afford polycarbonate block copolymers. Throughsequential addition of functionalized cyclohexene monomer, Coates, et.al. synthesized a multiblock polycyclohexene carbonate with differentfunctional substituents at the cyclohexene ring with Zn(II) diiminate ascatalyst (J. G. Kim, et. al., Macromolecules 2011, 44, 1110-1113).Similarly, Darensbourg et. al. reported that terpolymerization ofpropylene oxide, vinyl oxide and CO₂ provided random polycarbonatecopolymers of various compositions depending on the feed ratios of theepoxide monomers catalyzed by binary and bifunctional (salen) Co(III)complexes, the vinyl group introduced could be crosslinked afterwards(D. J. Darensbourg, et. al., Polymer Chemistry 2014, DOI:10.1039/c4py01612b). Due to the high selectivity of catalysts to onekind of epoxide monomer, other strategy had to be employed to get blockcopolymers other than polycarbonates. Using various polymers containinghydroxyl or carboxylic group as a chain transfer agents, Lee et. al.synthesized block copolymers of PPC, and poly(ethylene oxide),polytetrahydrofuran, polycaprolactone, polystyrene, etc. respectively(A. Cyriac, et al, Macromolecules 2010, 43, 7398-7401). Alternatively,Williams's and Lu's group reported the preparation of polycarbonateblock copolymer in a two-step process, the end or side hydroxyl groupsdue to transfer or hydrolysis of polycarbonate produced in the firststep, subsequently initiate the polymerization of lactide; ABA-type andgrafted polycarbonate-b-polylactide were obtained respectively (M. R.Kember, et al, Polymer Chemistry 2012, 3, 1196-1201; Y. Liu, et al,Macromolecules 2014, 47, 1269-1276). Recently, Darensbourg havedemonstrated a tandem catalytic approach for the synthesis of AB diblockcopolymers containing poly(styrene carbonate) and polylactide, where theend hydroxyl group of macroinitiator was generated at the end ofcopolymerization of styrene oxide/CO₂ copolymerization (G.-P. Wu, et al,J. Am. Chem. Soc. 2012, 134, 17739-17745); in another strategy, theyreported the synthesis of ABA-type PLA-PPO-PLA triblock copolymers inone pot, here, water was added along with the propylene oxide (PO)/CO₂copolymerization process as a chain-transfer reagent (D. J. Darensbourg,G. P. Wu, Angew. Chem. Int. Ed. 2013, 52, 10602-10606).

Recently, more attention has been paid to green processes and catalystsbased on main group metal complexes. With efficient catalysts such asCo(III) and Cr(III), the traces of metal residues inside the resin mayresult in toxic, colored, degradation issues that will affect theirperformance and limit their applications accordingly. In contrast,aluminum, one of the earliest investigated metal as catalyst since thediscovery of copolymerization of CO₂ and epoxides, is earth-abundant,cheap, and biocompatible. More importantly, aluminum complexes are knownto catalyze a wide range of other polymerization reactions, thusproviding the possibility to expand CO₂ based block copolymers otherthan epoxides. In fact, due to the competitive homopolymerization ofepoxides catalyzed by aluminum catalysts, more work needs to be done toimprove the catalytic effects. Aluminum porphyrin complex and Schiffbase complexes both could catalyze alternating copolymerization of CO₂and epoxides, the catalytic efficiencies were quite low, and molarmasses of obtained polycarbonates were below 10 Kg mol⁻¹ (N. Ikpo, J. C.Flogeras, F. M. Kerton, Dalton Trans., 42, 2013, 8998-9006). As foraluminum alkoxides Rtriisopropoxide (T. A. Zevaco, et. al. Green Chem.,2005, 7, 659-666); bisphenoxide (T. A. Zevaco, et. al. Catal. Today,2006, 115, 151-161); calixarenoxide (W. Kuran, et. al. J. Macromol.Sci., Pure Appl. Chem., 1998, A35, 427-437)], these relatively simplecoordination complexes, however, required high pressures, the achievedpolymers were of low to moderate carbonate linkage with low molar mass.The only exception is the results reported by Kerton (N. Ikpo, et. al.Organometallics, 2012, 31, 8145-8158) that a relatively high molecularweight polymer (20.9 Kg mol-1) with 54% of carbon dioxide incorporationwas achieved when amine-phenoxide was used as catalyst.

The composition of carbonate linkage in these systems could be hardlyfine-tuned once the catalysts for the copolymerization of CO₂ andepoxides were chosen, which then yielded for each system a fixedpercentage of carbonate linkage between 100% and a few percent. The onlymeans in each of these systems to vary the percentage of carbonatelinkage would thus be to vary the pressure of CO₂ or the temperature.For some purposes, polymers whose level of carbonate linkages could beeasily varied may also be desirable. However, one example that allowstuning of the composition of carbonate linkage is reported by Lee et.al. who mixed two kinds of catalysts in different ratio, the propagationoccurring through shuttling of the growing polymer chains between thetwo catalyst sites: Salen-cobalt(III) complex bearing four quaternaryammonium salts [a highly active poly(propylene carbonate) catalyst, 100%of carbonate linkage] and a double metal cyanide [DMC, a highly activepoly(propylene oxide), 10% of carbonate linkage], copolymers with 10-67%of carbonates could be achieved (J. K. Varghese, et al, Polyhedron 2012,32, 90-95).

SUMMARY

In general, embodiments of the present disclosure describe, among otherthings, initiating systems, methods of making polycarbonates, andmethods of controlling polymer composition.

Embodiments of the present disclosure describe initiating systemscomprising an activator and an initiator, wherein the activator includesan alkyl borane or alkyl aluminum, wherein the initiator includes anorganic cation and either an alkali metal or a compound containing anactive protic hydrogen.

Embodiments of the present disclosure further describe methods of makinga polycarbonate comprising contacting a cyclic monomer and carbondioxide in the presence of an activator and an initiator to form apolycarbonate, wherein the activator is one or more of an alkyl boraneand alkyl aluminum, wherein the initiator includes an organic cation andeither an alkali metal or a compound containing an active protichydrogen.

Embodiments of the present disclosure also describe methods of making apolycarbonate comprising contacting an epoxide monomer and carbondioxide in the presence of an activator and an initiator to form apolycarbonate, wherein the activator is trialkyl borane, wherein theinitiator includes an alkali metal and an organic cation.

Embodiments of the present disclosure also describe methods of making apolycarbonate comprising contacting an epoxide monomer and carbondioxide in the presence of an activator and an initiator to form apolycarbonate, wherein the activator is a trialkyl borane, wherein theinitiator includes an alcohol compound and an organic cation.

Other embodiments of the present disclosure describe methods of makingblock copolymers of polycarbonate comprising contacting a first epoxidemonomer and carbon dioxide in the presence of an activator includingtrialkyl borane and an initiator to form a first polycarbonate block,and adding a second epoxide monomer to form a second polycarbonate blockof a block copolymer that is different from the first polycarbonateblock

Embodiments of the present disclosure further describe a method ofcontrolling a polymer composition, comprising contacting one or morecyclic monomers and carbon dioxide; adjusting an amount of one or moreof a Lewis acid catalyst, an ionic liquid, and an initiator in thepresence of the one or more cyclic monomers and carbon dioxide,sufficient to selectively modify a resulting polycarbonate; andagitating, sufficient to copolymerize the one or more cyclic monomersand carbon dioxide to create the polycarbonate.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings illustrate non-limiting example embodiments ofthe invention.

FIG. 1 is a flowchart of a method of making polycarbonates, according toone or more embodiments of the present disclosure.

FIG. 2 is a flowchart of a metal-based method of making polycarbonates,according to one or more embodiments of the present disclosure.

FIG. 3 is a flowchart of a metal-free method of making polycarbonates,according to one or more embodiments of the present disclosure.

FIG. 4 is a flowchart of a method of making a block copolymer ofpolycarbonate, according to one or more embodiments of the presentdisclosure.

FIG. 5 illustrates a block flow diagram of a method of making apolycarbonate, according to one or more embodiments of this disclosure.

FIG. 6 illustrates a block flow diagram of a method of controlling apolymer composition, according to one or more embodiments of thisdisclosure.

FIG. 7 shows Gel Permeation Chromatography (GPC) traces ofpoly(cyclohexene carbonate) (PCHC) prepared by alkyllithium/Phosphazenecomplexes (THF, polystyrene standards), according to one or moreembodiments of the present disclosure.

FIG. 8 shows GPC traces of poly(propylene carbonate) (PPCs) prepared byalkyllithium/Phosphazene complexes (THF, polystyrene standards),according to one or more embodiments of the present disclosure.

FIG. 9 shows GPC traces of poly(ethylene carbonate) (PECs) prepared byalkyllithium/Phosphazene complexes (GPC calibrated with polystyrenestandards in chloroform), according to one or more embodiments of thepresent disclosure.

FIG. 10 shows GOC traces of Pt-BuCs prepared by alkyllithium/Phosphazenecomplexes (THF, polystyrene standards), according to one or moreembodiments of the present disclosure.

FIG. 11 shows GPC traces of PCHC prepared by LiCl/Phosphazene complexes(THF, polystyrene standards), according to one or more embodiments ofthe present disclosure.

FIG. 12 shows ¹H NMR characterization of poly(cyclohexene carbonate)prepared by alkylithium/Phosphazene complexes (400 MHz, Chloroform-d),according to one or more embodiments of the present disclosure.

FIG. 13 shows ¹H NMR characterization of poly(cyclohexene carbonate)prepared by LiCl/Phosphazene complexes (400 MHz, Chloroform-d),according to one or more embodiments of the present disclosure.

FIG. 14 shows ¹H NMR characterization of poly(ethylene carbonate)prepared by alkylithium/Phosphazene complexes (400 MHz, Chloroform-d),according to one or more embodiments of the present disclosure.

FIG. 15 shows ¹H NMR characterization of poly(propylene carbonate)prepared by alkylithium/Phosphazene complexes (400 MHz, Chloroform-d),according to one or more embodiments of the present disclosure.

FIG. 16 shows ¹H NMR characterization of poly(styrene carbonate)prepared by alkylithium/Phosphazene complexes (400 MHz, Chloroform-d),according to one or more embodiments of the present disclosure.

FIG. 17 shows MALD-TOF characterization of PCHC, the main populationwith peak to peak difference of 142 corresponding to the alternatingstructure, according to one or more embodiments of the presentdisclosure.

FIG. 18 shows infrared spectroscopy of poly(cyclohexene carbonate) withhigh selectivity (100% polymer) and no cyclic carbonates formed,according to one or more embodiments of the present disclosure.

FIG. 19 is a graphical view of GPC traces of PCHCs (entry 9, 10, and 11in Table 1) prepared by alkyllithium/phosphazene complexes, according toone or more embodiments of the present disclosure.

FIG. 20 is a graphical view of ¹H NMR spectrum of poly(cyclohexenecarbonate) prepared by alkyllithium/phosphazene complexes (entry 9 intable 1), according to one or more embodiments of the presentdisclosure.

FIG. 21A is a graphical view of GPC trace entry 2 in table 2, accordingto one or more embodiments of the present disclosure.

FIG. 21B is a graphical view of ¹H NMR spectrum of poly(ethylenecarbonate) (entry 2 in table 2), according to one or more embodiments ofthe present disclosure.

FIG. 22A is a graphical view of GPC trace of entry 7 in table 2,according to one or more embodiments of the present disclosure.

FIG. 22B is a graphical view of ¹H NMR spectrum of poly(propylenecarbonate) (entry 7 in table 2), according to one or more embodiments ofthe present disclosure.

FIG. 23 is a graphical view of GPC trace of entry 14 in table 2,according to one or more embodiments of the present disclosure.

FIG. 24 is a graphical view of 41 NMR spectrum of poly(butylenecarbonate) (entry 14 in table 2), according to one or more embodimentsof the present disclosure.

FIG. 25 is a graphical view of GPC trace of entry 16 in table 2,according to one or more embodiments of the present disclosure.

FIG. 26 is a graphical view of 41 NMR spectrum of poly(hexene carbonate)(entry 16 in table 2), according to one or more embodiments of thepresent disclosure.

FIG. 27 is a graphical view of GPC trace of entry 20 in table 2,according to one or more embodiments of the present disclosure.

FIG. 28 is a graphical view of 41 NMR spectrum of poly(octane carbonate)(entry 20 in table 2), according to one or more embodiments of thepresent disclosure.

FIG. 29 is a graphical view of GPC trace of entry 26 in table 2,according to one or more embodiments of the present disclosure.

FIG. 30 is a graphical view of ¹H NMR spectrum of poly(styrenecarbonate) (entry 26 in table 2), according to one or more embodimentsof the present disclosure.

FIG. 31 is a graphical view of GPC trace of entry 28 in table 2,according to one or more embodiments of the present disclosure.

FIG. 32 is a graphical view of ¹H NMR spectrum of poly(cyclohexenecarbonate) (entry 28 in table 2), according to one or more embodimentsof the present disclosure.

FIG. 33 is a graphical view of GPC trace of entry 29 in table 2,according to one or more embodiments of the present disclosure.

FIG. 34 is a graphical view of ¹H NMR spectrum of poly(allyl glycidylcarbonate) (entry 29 in table 2), according to one or more embodimentsof the present disclosure.

FIG. 35 is a graphical view of GPC trace of entry 32 in table 2,according to one or more embodiments of the present disclosure.

FIG. 36 is a graphical view of ¹H NMR spectrum of poly(butyl glycidylcarbonate) (entry 32 in table 2), according to one or more embodimentsof the present disclosure.

FIG. 37 is a graphical view of GPC trace of entry 0 and entry 4 in table3, according to one or more embodiments of the present disclosure.

FIG. 38 is a graphical view of ¹H NMR spectrum of poly(CHC-b-HC-b-CHC(entry 4 in table 3), according to one or more embodiments of thepresent disclosure.

FIG. 39A illustrates a graphical view of an infrared (IR) degradationcharacterization of a prepared polymer initiated by N-heterocycliccarbene (NHC), according to one or more embodiments of this disclosure.

FIG. 39B illustrates a graphical view of a gel permeation chromatography(GPC) degradation characterization of a prepared polymer initiated byN-heterocyclic carbene (NHC), according to one or more embodiments ofthis disclosure.

FIG. 40 illustrates a graphical view of an infrared (IR) degradationtest of prepared polymer initiated by imidazolium chloride, according toone or more embodiments of this disclosure.

FIG. 41A illustrates a graphical view of NMR characterization ofprepared poly(cyclohexene carbonate) initiated by Lithium benzoxide andcatalyzed by triisobutyl aluminum, according to one or more embodimentsof this disclosure.

FIG. 41B illustrates a graphical view of MALDI-tof characterization ofprepared poly(cyclohexene carbonate) initiated by Lithium benzoxide andcatalyzed by triisobutyl aluminum, according to one or more embodimentsof this disclosure.

FIG. 42A illustrates a graphical view of NMR characterization ofprepared poly(cyclohexene carbonate) initiated by Lithium chloride andcatalyzed by triisobutyl aluminum, according to one or more embodimentsof this disclosure.

FIG. 42B illustrates a graphical view of MALDI-tof characterization ofprepared poly(cyclohexene carbonate) initiated by Lithium chloride andcatalyzed by triisobutyl aluminum, according to one or more embodimentsof this disclosure.

FIG. 43A illustrates a graphical view of NMR characterization ofprepared poly(cyclohexene carbonate) initiated by Lithium bromide andcatalyzed by triisobutyl aluminum, according to one or more embodimentsof this disclosure.

FIG. 43B illustrates a graphical view of MALDI-tof characterization ofprepared poly(cyclohexene carbonate) initiated by Lithium bromide andcatalyzed by triisobutyl aluminum, according to one or more embodimentsof this disclosure.

FIG. 44 illustrates a graphical overlay view of a gel permeationchromatography (GPC) characterization of prepared poly(cyclohexenecarbonate) initiated by lithium salts and catalyzed by triisobutylaluminum, according to one or more embodiments of this disclosure.

FIG. 45 illustrates a graphical view of NMR characterization of preparedpoly(cyclohexene carbonate) initiated by Lithium triethylene glycoxideand catalyzed by triisobutyl aluminum, according to one or moreembodiments of this disclosure.

FIG. 46 illustrates a graphical overlay view of a gel permeationchromatography (GPC) characterization of prepared poly(cyclohexenecarbonate) initiated by lithium glycoxides and catalyzed by triisobutylaluminum, according to one or more embodiments of this disclosure.

FIG. 47 illustrates a graphical view of NMR characterization of preparedpoly(propylene carbonate) initiated by Lithium triethylene glycoxide andcatalyzed by triisobutyl aluminum, according to one or more embodimentsof this disclosure.

FIG. 48 illustrates a graphical view of a gel permeation chromatography(GPC) characterization of prepared poly(propylene carbonate) initiatedby lithium triethylene glycoxides and catalyzed by triisobutyl aluminum,according to one or more embodiments of this disclosure.

FIG. 49 illustrates a graphical view of NMR characterization of preparedpolymer initiated by Lithium polystyrene and catalyzed by triisobutylaluminum, according to one or more embodiments of this disclosure.

FIG. 50 illustrates a graphical overlay view of a gel permeationchromatography (GPC) characterization of prepared polymers initiated bylithium polystyrene and catalyzed by triisobutyl aluminum, according toone or more embodiments of this disclosure.

FIG. 51 illustrates a graphical view of NMR characterization of preparedpolymer initiated by potassium tertbutyloxide and catalyzed by triethylborane, according to one or more embodiments of this disclosure.

FIG. 52 illustrates a graphical view of NMR characterization of preparedpolymer initiated by tetrabutylammonium chloride and catalyzed bytriethyl borane, according to one or more embodiments of thisdisclosure.

FIG. 53 illustrates a graphical view of NMR characterization of preparedpolymer initiated by benzene alcohol and phosphazene P2 and catalyzed bytriethyl borane, according to one or more embodiments of thisdisclosure.

FIG. 54 illustrates a graphical view of NMR characterization of preparedpolymer initiated by benzene alcohol and phosphazene P4 and catalyzed bytriethyl borane, according to one or more embodiments of thisdisclosure.

FIG. 55 illustrates a graphical view of NMR characterization of preparedpoly(cyclohexene carbonate) initiated by potassium tertbutyloxide andcatalyzed by triethyl borane, according to one or more embodiments ofthis disclosure.

FIG. 56 illustrates a graphical overlay view of a gel permeationchromatography (GPC) characterization of prepared poly(propylenecarbonate) and poly(cyclohexene carbonate) polymers catalyzed bytriethylborane, according to one or more embodiments of this disclosure.

FIGS. 57A-57B are a schematic diagram of preparingn-butyllithium/phosphazene P₄-t-Bu superbase complex and H¹ NMR spectrafor n-BuLi/P₄-t-Bu complex (400 MHz, benzene-d₆), according to one ormore embodiments of the present disclosure.

DETAILED DESCRIPTION

The invention of the present disclosure relates to initiating systemsfor the synthesis of polycarbonates and methods of synthesizingpolycarbonates. The synthesis of polycarbonates may include thecopolymerization (e.g., anionic copolymerization) of carbon dioxide andepoxide monomers in the presence of an activator and an initiator, whichmay collectively be referred to as an initiating system. The activatormay include one or more of an alkyl borane or alkyl aluminum. Forexample, the activator may include a trialkyl borane, such as triethylborane, or a trialkyl aluminum, such as triisobutyl aluminum. Theinitiator may include an organic cation and either an alkali metal oralcohol compound. For example, the organic cation may include one ormore of ammonium, phosphonium, and phosphazenium; the alkali metal mayinclude one or more of lithium, potassium, and sodium; and the alcoholcompound may include any compound containing more than one hydroxylgroup. Together, the activator and initiator may be used as aninitiating system to produce polycarbonates from a wide array of epoxidemonomers. In addition, the initiating systems may be used to produce,among other things, AB and/or ABA block copolymers of polycarbonate,where polycarbonate block A is different from polycarbonate block B.

The methods of the present disclosure provide various synthetic routesthat are simple, scalable, and modifiable. The methods do not requiremulti-step synthetic routes for activator/ligand. In addition, thesynthesis of polycarbonates may include anionic copolymerization ofepoxide monomer and carbon dioxide to afford perfectly or nearlyperfectly alternating polycarbonates. In embodiments in which there isno solvent, the methods produce polymers of high clarity for bulkpolymerizations. The synthesis of block copolymers may includesequential addition of epoxide monomers to afford, for example, ABdiblock copolymers and ABA triblock copolymers. The methods may also beused to produce non-linear complex macromolecular architectures, diolpolycarbonates, polyester, and polyether, among other things. Themethods permit precise control over the molecular weight ofpolycarbonates, which is essential for practical applications ofpolymerization process and obtaining desired physical properties.

In addition, the synthetic routes for polycarbonates and/orpolycarbonate block copolymers may proceed either in the presence of ametal or under metal-free conditions. For example, in some embodiments,a metal-based synthetic route may be used for the synthesis ofpolycarbonates. In these embodiments, the initiating system may includea phosphazene base as the organic cation and lithium as the alkalimetal. In other embodiments, the synthesis of polycarbonates may proceedunder metal-free conditions, obviating any post-synthesis purificationsteps. In these embodiments, the initiating system only needs to includean organic cation and borane as an activator for the copolymerization toproceed metal-free. Metal-free conditions may be a desirable alternativebecause the polycarbonate is color-free and generally about 100% solid.In these ways, the initiating systems provide unprecedented performanceand versatility in the synthesis of polycarbonates and ABA blockcopolymers of polycarbonates from a wide array of epoxide monomers undervarious conditions and via numerous synthetic routes.

Further, common commercial problems with polycarbonates includelaborious and costly activator preparation, as well as residuesremaining in the resins. These problems may increase costs, createtoxicity issues, and limit performance. Importantly, there lacks amethodology to tune the carbonate contents for specific applications.The activators for the copolymerization of CO₂ and epoxides in thepresent disclosure are inexpensive and widely available, can tune thecomposition of obtained polycarbonates, and copolymerize with othercyclic monomers, such as lactide and caprolactones.

The methods and compositions disclosed herein also provide inexpensive,commercially available, biocompatible Lewis acids as activators forcopolymerization of carbon dioxide and cyclic monomers, such asepoxides. Further, the carbonate and polyether contents can beconveniently adjusted based on the feeding ratio of activator toinitiator or together with amount of ionic liquid and lithium saltsutilized. Polycarbonates can be modified or tuned according toembodiments of the invention to create two types of block copolymerstructure, random and alternated copolymer with the carbonatecomposition from about 2% to about 100%, for example.

As embodiments of this disclosure discuss preparations of polycarbonatewith different compositions and structures, which is also the precursorof polyurethane, results may find application in packaging, coatings,surfactant, and medical industries.

Definitions

As used herein, “polycarbonate” refers to a general class of polymerscontaining a carbonate moiety.

As used herein, “contacting” refers to bringing two or more componentsin proximity, such as physically, chemically, electrically, or somecombination thereof. Mixing is an example of contacting.

As used herein, “agitating” refers to disturbing or moving components.Agitating can include stirring and shaking, for example.

As used herein, “ionic liquid” refers to a salt in a liquid state. In anionic liquid, the ions are poorly coordinated and result in the liquidshaving low melting points. Ionic liquids can be derived frommethylimidazolium and pyridinium ions, for example.

As used herein, “lithium salt” refers to a salt with lithium as acation. They include inorganic and organic salts, and could participatein polymerization as an initiator or as additive to tune thepolymerization activity of one or more monomers and carbon dioxide.

As used herein, “initiating system” refers to a system including atleast one initiator and activator.

As used herein, “initiator” refers to a mono- or poly- (includingmacromolecular) alcoholic, phenolic, acidic salts with cations (lithium,sodium, potassium, cesium, ammonium, imidazolium, phosphazium) producedthrough deprotonation by different bases, salts, and other lithium saltsadditives, as well as superbase complexes. Bases include, but are notlimited to, for example, imidazolium alkoxide, lithium alkoxide, lithiumphenolate, and alkyllithium (including macromolecular alkoxide); saltsinclude, but are not limited to, for example, imidazolium halide,lithium, sodium, potassium, halides, ammonium, tetraalkylammonium,tetraalkylphosphonium in halide, hydroxide, carbonate, and carboxylate;and other lithium salts additives include, but are not limited to, forexample, lithium carbonate, LiOH, LiCO₃, LiClO₄, LiPF₆, LiBF₄, andlithium bis(trifluoromethane)sulfonamide (Tf2N). The initiator caninclude macromolecular salts, including, but not limited to, forexample, one or more of macromolecular lithium salts. The initiator caninclude an anionic nucleophile.

As used herein, “epoxide” refers to a cyclic ether with a three-atomring. Examples of epoxides include propylene oxide (PO) and cyclohexeneoxide (CHO), and can be used as cyclic monomers.

Initiating Systems

Embodiments of the present disclosure describe initiating systemsincluding at least one activator and initiator for use in the synthesisof polycarbonates and/or block copolymers of polycarbonate from thecopolymerization of one or more cyclic monomers and carbon dioxide.While conventional initiating systems are limited to a small number ofepoxides, the initiating systems of the present disclosure may be usedto synthesize polycarbonates from a wide array of epoxides. For example,the initiating systems may be used in the anionic copolymerization ofcyclic monomers (e.g., epoxide monomers) and carbon dioxide to formperfectly (or nearly perfectly) alternating polycarbonates. Theinitiating systems may also be used to synthesize block copolymers ofpolycarbonate. In many embodiments, the block copolymers may becharacterized as AB or ABA block copolymers, wherein the A block and Bblock are different polycarbonate blocks.

The activator may include one or more of boron and aluminum compounds.For example, the activator may include one or more of an alkyl boraneand alkyl aluminum. In embodiments in which the activator includes analkyl borane, the activator may include a trialkyl borane. For example,trialkyl boranes may include one or more of triethyl borane, trimethylborane, triisobutylborane, and triphenyl borane. In embodiments in whichthe activator includes an alkyl aluminum, the activator may include atrialkyl aluminum. For example, the trialkyl aluminum may includetriisobutyl aluminum.

The initiator may include salts or an organic cation associated with analcohol compound forming an organic base or an alkali metal associatedwith an alcohol compound (RO or an alkali metal such as Li+ associatedwith an alcohol compound mixed with a superbase P₁, P₂ or P₄. Theorganic cation may be based on one or more of phosphazenium, ammonium,and/or phosphonium. For example, the organic cation/organic base may beobtained by mixing phosphazene bases (e.g., t-Bu-P_(Y), where Y is 1, 2,or 4) with an alcohol, or may include bis (triphenylphosphoranylidene)ammonium chloride, tetraoctylammonium chloride, and tetrabutylammoniumchloride. In other embodiments, the organic cation may include anyammonium or phosphonium salt, wherein the nitrogen or phosphorous,respectively, are connected by four alkyl groups, each of which may bethe same or different. The alkali metal may include one or more oflithium, potassium, and sodium. The alcohol compound may include anycompound containing more than one hydroxyl group such as a diol and/ortriol. The alcohol compound may be a linear polymer or a star-branchedpolymer. In many embodiments, the alcohol compound may include1,4-dibenzenemethanol. In other embodiments, any compound containing anactive protic hydrogen may be used, including, but not limited to, oneor more of alcohols, thiols, phenols, carboxylic acids, etc.

In an embodiment, the initiator may be a salt, such as LiCl, LiBr,and/or any other salt disclosed herein. In an embodiment, the initiatormay be an organic cation associated with an alcohol, such as RO⁻, N⁺(Alkyl)₄ and/or any other embodiment disclosed herein that includes anorganic cation associated with an alcohol. In an embodiment, theinitiator may include an alkali metal cation associated with an alcohol,such as RO⁻, Li⁺ and/or any other embodiment disclosed herein thatincludes an alkali metal cation associated with an alcohol. In anembodiment, the initiator may include an alkali metal, such as Li⁺,associated with an alcohol compound mixed with a superbase, such as RO⁻,Li—P₄ ⁺, and/or any other embodiment disclosed herein that includes analkali metal associated with an alcohol compound mixed with a superbase.

The activator and initiator may comprise the initiating system. In manyembodiments, it is important to provide the activator in excess ofstoichiometric conditions. For example, the initiator (e.g., base, suchas BuLi, oxyanion, etc.) and activator (e.g., Lewis acid) may reactunder stoichiometric conditions to form an ate complex (e.g., theinitiating system). The ate complex may be used to initiate thecopolymerization of epoxides and CO₂. The ate complex may be formed whena Lewis acid gains one bond by reaction with a base and becomes anegative anion. Similarly, when the base reacts with an acid, it gainsone bond and becomes a positive cation (e.g., phophazene base, P₄,reacting with H⁺ of an alcohol becomes a positive cation, P₄—H⁺; in thepresence of Li⁺, P₄ gives the P₄—Li⁺, a positive cation). See thereaction below, for example, where the central boron atom gains one morebond and becomes a negative anion, reducing the reactivity of atecomplex formed.RO⁻,M⁺+B(Alkyl)₃→[ROB(Alkyl)₃]⁻,M⁺The initiator of the ate complex (i.e., initiating system) may be usedto activate carbon dioxide. The activator of the ate complex (i.e.,initiating system) may be used to activate the epoxide monomer. However,since the activator reacted with the base under stoichiometricconditions in forming the ate complex, in many embodiments, it isimportant to provide an excess of the activator in order to ensureactivation of the epoxide monomer. In some embodiments, where an excessof activator was not provided, no copolymerization may be occur.

Accordingly, the use of activators including boron and/or aluminum mayfulfill at least two important roles that are different from otheractivators known in the art. First, each of boron and/or aluminum may beused to form an ate complex with a growing anion for triggeringpolymerization. The reactivity of these ate complexes is very differentfrom conventional anions because ate complexes are the result of thereaction of the latter anions with Lewis acids; ate complexes thereforeexhibit a lower reactivity than the bases they are generated from andare generally more selective. Second, trialkyl boron and/or trialkylaluminum is used in excess of the organic cation and/or initiator tospecifically activate the epoxide monomer in a ratio that may vary from1.1:1 to 10:1. For example, a 1:1 ratio of boron or aluminum to organiccation or initiator may fail to activate the monomer and result in nopolymerization. In many embodiments, a 1:2 ratio of organiccation/initiator to boron/aluminum is appropriate to activate themonomer.

Some embodiments of the present disclosure describe an initiating systemcomprising an activator including an alkyl borane and an initiatorincluding an organic cation and alkali metal. The alkyl borane mayinclude a trialkyl borane. For example, the trialkyl borane may includetriethyl borane (shown below), an organoborane with a B—C bond andgenerally a colorless pyrophoric liquid:

The addition of triethylborane may provide numerous advantages overconventional activators. For example, in reaction systems for theanionic alternating copolymerization of epoxides with CO₂, triethylborane may serve at least two important functions (1) for epoxidemonomers activation and (2) for generating ate complexes by reactionwith a base (e.g., BuLi, oxyanion, etc.) thereby making the activespecies formed more selective. Accordingly, triethyl borane, among otheractivators, may not only be used as an activator of an epoxide monomer,but it may also be used to generate less reactive and yet more selectivechain ends.

The initiator may be used to generate highly reactive anionic speciesand/or to capture/activate carbon dioxide. In many embodiments, theinitiator may be prepared from and/or include a phosphazene base (e.g.,as organic cation) and one or more of an alkyllithium, lithium alkoxide,and lithium salt (e.g., as source of alkali metal). The phosphazene baseand lithium c: lion may be mixed to form the cation P₄—Li⁺ which in turnmay enhance the reactivity of the associated anion responsible for thecopolymerization of epoxides and CO₂. The organolithium compounds areunique among organic compounds with alkali metals because the C—Li bondexhibits properties of both covalent and ionic bonds. In someembodiments, this is observed because lithium, as compared to otheralkali metals, has the smallest radius, the highest electronegativity,and the highest ionization potential.

The initiator may generally be characterized by the following formula:X⁻, Cat⁺, where X is R—O⁻, R—C⁻, Cl⁻, F⁻, Br⁻, CO₂ ⁻ or CO₃ ⁻; and Cat⁺may be Li⁺, Na⁺, K⁺, Cs⁺, or an organic cation such as ammonium orphosphonium cation, or a cation resulting from the mixing of aphosphazene base (P_(y)) with cation such as Li⁺ which generatesP_(y)—Li⁺ where Y may be 1, 2, or 4.

In some embodiments, the initiator may be prepared from and/or includean alkyllithium and the phosphazene base. The alkyllithium may includeone or more of n-BuLi and sec-BuLi. In these embodiments, thealkyllithium-based initiator may be characterized by the formula:R—C⁻{⁺Li/t-Bu-P_(Y)}, R—C⁻ may be any alkyl or any “living” polymerobtained by anionic polymerization of vinyl monomers and carrying anend-standing carbanion: for example polystyrenyl lithium, polyisoprenyllithium, etc.

In other embodiments, the initiator may be prepared from and/or includea lithium alkoxide and the phosphazene superbase. In these embodiments,the lithium alkoxide-based initiator may be characterized by theformula: R—O⁻{⁺Li/t-Bu-P_(Y)}, where R—O⁻ is an anion of any lithiumalkoxide. RO⁻ may be any small molecular organo-alcoholate or anymacromolecule terminated with an alcoholate, such as one or more ofPSt-O⁻ (PS=polystyrene), PI—O⁻ (PI=polyisoprene), PEO—O⁻(PEO=polyethylene oxide), and PPO⁻ (PPO=polypropylene oxide).

Other embodiments may include an initiator that may be prepared fromand/or include a lithium salt (e.g., LiCl, LiBr, LiF, and Li₂CO₃) andthe phosphazene base. In these embodiments, the lithium salt-basedinitiator may be characterized by the formula: X⁻{⁺Li/t-Bu-P_(Y)}, whereX is one or more of Cl, Br, F, and CO₃.

Non-limiting examples of suitable and/or preferred alkyllithiums,lithium alkoxides, lithium salts, and phosphazene bases are providedbelow:

Non-limiting examples of initiators may include one or more ofn-Bu⁻{⁺Li/t-Bu-P₄}, n-Bu⁻{⁺Li/t-Bu-P₂}, sec-Bu⁻{⁺Li/t-Bu-P₄}, andCl⁻{⁺Li/t-Bu-P₄}.

Some embodiments of the present disclosure describe an initiating systemcomprising an activator including an alkyl borane and an initiatorincluding an organic cation and an alcohol compound. The alkyl boranemay include a trialkyl borane. For example, the trialkyl borane mayinclude triethyl borane. The organic cation may include a phosphazenebase, such as t-Bu-P_(Y), where Y is 1, 2, or 4; and the alcoholcompound may include any compound, including those of macromolecularsize, containing more than one hydroxyl group. The alcohol compound mayinclude a diol and/or triol. For example, the alcohol compound mayinclude 1,4-benzenedimethanol. In other embodiments, any compoundcontaining an active protic hydrogen may be used, including, but notlimited to, one or more of alcohols, thiols, phenols, carboxylic acids,etc.

Methods of Making Polycarbonates

Embodiments of the present disclosure also describe methods of makingpolycarbonates using the initiating systems described herein. Inparticular, FIG. 1 is a flowchart of a method of making polycarbonates,according to one or more embodiments of the present disclosure. Themethod 100 may comprise contacting 106 one or more cyclic monomers 102and carbon dioxide 104 in the presence of an activator and an initiator108 to form a polycarbonate 110. The activator may include one or moreof an alkyl borane and alkyl aluminum. The initiator may include atleast an organic cation and either an alkali metal or an alcoholcompound. Any of the activators, initiators, and/or initiating systemsof the present disclosure may be used to form polycarbonates accordingto any of the methods of the present disclosure. For example, in someembodiments, any compound containing an active protic hydrogen (e.g.,thiols, phenols, carboxylic acids, etc.) are used in place of an alcoholcompound.

The polycarbonates may be produced under metal-free conditions or viametal-based synthetic routes. Metal-based synthetic routes may includeactivators including an alkali metal. Such metal-based activators (e.g.,activators based on) may be desirable because they exhibit highselectivity and high selectivity toward the alternating insertion ofcarbon dioxide and epoxides. On the other hand, metal-based syntheticroutes may be toxic and produce colored products. In addition,metal-based synthetic routes require multi-step processes, as well as astep for post-polymerization metal removal. Accordingly, metal-freeconditions may be a desirable alternative to metal-based syntheticroutes. Accordingly, the copolymerization of epoxide monomer and carbondioxide may proceed under metal-free conditions. In particular, thecopolymerization may proceed under metal-free conditions in anyembodiment including boron as an activator and an organic cation as aninitiator.

The one or more cyclic monomers may include any cyclic ether and/orcyclic ester. The cyclic ethers may include any epoxide. For example, inmany embodiments, the one or more cyclic monomers may include one ormore of ethylene oxide, propylene oxide, 1-butene oxide, 1-hexene oxide,1-octene oxide, styrene oxide, cyclohexene oxide, allyl glycidyl ether,and butyl glycidyl ether. In other embodiments, the one or more cyclicmonomers include cyclic esters. For example, the cyclic esters mayinclude lactides and/or caprolactones.

Contacting the one or more cyclic monomers (e.g., epoxide(s)) and carbondioxide in the presence of at least the activator and initiator formsthe polycarbonate. The contacting generally refers to bringing two ormore components into proximity, such as physical and/or chemicalproximity. In many embodiments, contacting may include adding and/ormixing two or more components in a reaction vessel and/or charging achamber including the reaction vessel with a gaseous componentsufficient to bring at least two of the components into physical and/orchemical proximity. The contacting may occur at temperatures rangingfrom about room temperature to about 120° C. and at pressures rangingfrom about atmospheric pressure to about 30 bar. In many embodiments,the temperature ranges from about −30° C. to about 80° C. and thepressure is about 20 bar.

The resulting polycarbonate may include any polymer containing acarbonate group. In many embodiments, the polycarbonate is analternating copolymer formed from the anionic copolymerization of anepoxide monomer and carbon dioxide. The polycarbonates producedaccording to the methods of the present disclosure may be perfectlyalternating polycarbonates and/or nearly perfectly alternatingpolycarbonates. The polycarbonate may, for example, be an alternatingcopolymer of one or more of poly(cyclohexene carbonate), poly(propylenecarbonate), poly(ethylene carbonate), poly(styrene carbonate), andpoly(butylene carbonate).

As one example, a general synthetic route for the copolymerization ofepoxide monomer and carbon dioxide using initiating systems of thepresent disclosure is provided in Scheme 1:

where X is any halide, pseudohalide, alkoxide, phenoxide, carboxylate,carbonate, hydrogen carbonate, etc.; where each of R, R₁, R₂, R₃, R₄ isindependently one or more of any alkyl group including saturated andunsaturated, aromatic, cyclic alkyl group, heteroatom (e.g., halide, N₃,O, S, etc) containing alkyl groups.

Some embodiments of the present disclosure describe methods of makingpolycarbonates using specific initiating systems. In particular, FIG. 2is a flowchart of a metal-based method 200 of making a polycarbonate,according to one or more embodiments of the present disclosure. Themethod 200 comprises contacting 206 an epoxide monomer 202 and carbondioxide 204 in the presence of an activator including a trialkyl boraneand an initiator including an organic cation and an alkali metal 208form a polycarbonate 210. The epoxide monomer may include one or more ofpropylene oxide, cyclohexene oxide, ethylene oxide, styrene oxide, butylglycidyl ether, and allyl glycidyl ether. The activator may include oneor more of triethyl borane, trimethyl borane, triisobutylborane, andtriphenylborane. In many embodiments, the activator is triethyl borane.

The initiator may include an organic cation or an alkali metal. Whileany of the organic cations and/or alkali metals described herein may beused, in some embodiments, the initiating system may be characterized bythe following formula:R—O⁻Cat⁺where R—O⁻is an alkoxide anion and Cat⁺ may be Li⁺, Na⁺, K⁺, Cs⁺, or anorganic cation such as ammonium or phosphonium cation, or a cationresulting from the mixing of a phosphazene base (P_(y)) with cation suchas Li⁺ which generates P_(y)—Li⁺ where Y may be 1, 2, or 4. RO mayinclude any compounds carrying terminal hydroxyls as describedpreviously. In some embodiments, the initiating system and/or complexinitiator may be characterized and/or referred to as a lithium alkoxide(R—OLi)/phosphazene base initiating system. As one example, thesynthetic route for the anionic alternating copolymerization of epoxidemonomer and carbon dioxide using the lithium alkoxide/phosphazene baseinitiating system to form a perfectly (or nearly perfectly) alternatingpolycarbonate is provided in Scheme 2:

As shown in Scheme 2, an alkylithium (e.g., n-BuLi) reacts with R—OH toform lithium alkoxides R—O⁻Li⁺ strong base, when a hydrogen atom isremoved from a hydroxyl group of an alcohol and reacts with a metal, andt-Bu-P₄ complexes with the lithium alkoxide R—O⁻Li⁺ to form a complexinitiator, RO⁻{⁺Li/t-Bu-P₄}, a highly reactive species, in the presenceof TEB.

In other embodiments, the initiating system may be characterized by thefollowing formula:R—C⁻{⁺Li/t-Bu-P_(Y)}where R—C⁻is one or more of n-Bu and sec-Bu and Y is 1, 2, or 4. Inthese embodiments, the initiating system and/or complex initiator may becharacterized and/or referred to as an alkylithium/phosphazene superbaseinitiating system. As one example, the synthetic route for the anionicalternating copolymerization of epoxide monomer and carbon dioxide usingthis initiating system to form a perfectly (or nearly perfectly)alternating polycarbonate is provided in Scheme 3:

As shown in Scheme 3, alkylithium reacts directly with t-Bu-P₄ to formn-Bu⁻{⁺Li/t-Bu-P₄}, a highly effective initiating system for anionicalternating copolymerization of CO₂ with epoxide monomers in thepresence of TEB.

In other embodiments, the initiating system may be characterized by thefollowing formula:X⁻{⁺Li/t-Bu-P_(Y)}where X is one or more of Cl, Br, F, and CO₃ and Y is 1, 2, or 4. Inthese embodiments, the initiating system and/or complex initiator may becharacterized and/or referred to as a lithium salt (LiX)/phosphazenesuperbase initiating system. As one example, the synthetic route for theanionic alternating coplymerization of epoxide monomer and carbondioxide using this initiating system to form a perfectly (or nearlyperfectly) alternating polycarbonate is provided in Scheme 4:

As shown in Scheme 4, lithium salts (e.g., LiCl, LiBr, LiF, and Li₂CO₃)react with t-Bu-P4 to form X⁻{⁺Li/t-Bu-P₄}, another highly effectiveinitiating system for anionic alternating copolymerization of CO₂ withepoxide monomers in the presence of TEB.

Any of the polycarbonates described herein may be formed according tothe methods of the present disclosure. In many embodiments, the methodmay be used to form polycarbonates with high molar masses, narrowmolecular weight distributions, and high carbonate linkage.Polycarbonates may be formed with higher molecular weights. For example,the molecular weight of the polycarbonates may range from about 25,000 gmol⁻¹ to about 250,000 g mol⁻¹. In some embodiments, the molecularweight of the polycarbonates may be about 40,000, about 75,000, or about250,000 g mol¹. In addition, the polycarbonates are not onlywell-defined, but also exhibit narrow molecular weight distributions andunimodal distributions. For example, the molecular weight distributionmay range from about 1.0 to about 1.5. In some embodiments, themolecular weight distribution may be about 1.1, about 1.2, or about 1.3.In addition, the carbonate linkage may range from about 75% to about100%. For example, the carbonate linkage may be greater than about 77%,greater than about 95%, or about 100%.

In one embodiment, the anionic copolymerization of cyclohexene oxide(CHO) with CO₂ affords perfectly alternating poly(cyclohexene carbonate)(PCHC) with carbonate linkage (100%), and molar mass up to 250, 0000 gmol⁻¹ with narrow molecular weight distribution (M_(w)/M_(n)<1.3). Inanother embodiment, the anionic copolymerization of propylene oxide (PO)with CO₂ affords perfectly alternating poly(propylene carbonate) (PPC)with higher carbonate linkage (>95%), and molar mass up to 75, 0000 gmol⁻¹ with narrow molecular weight distribution (M_(w)/M_(n)<1.1). Inanother embodiment, the anionic copolymerization of ethylene oxide (EO)with CO₂ affords perfectly alternating poly(ethylene carbonate) (PEC)with carbonate linkage (>77%), and molar mass close to 40, 0000 g mol⁻¹with narrow molecular weight distribution (M_(w)/M_(n)<1.2).

FIG. 3 is a flowchart of a metal-free method 300 of making apolycarbonate, according to one or more embodiments of the presentdisclosure. The method 300 comprises contacting 306 an epoxide monomer302 and carbon dioxide 304 in the presence of an activator including atrialkyl borane and an initiator including an organic cation and analcohol compound 308 to form a polycarbonate 310. The method of theseembodiments is generally metal free. The epoxide monomer may include oneor more of ethylene oxide, propylene oxide, 1-butene oxide, 1-hexeneoxide, 1-octene oxide, styrene oxide, cyclohexene oxide, allyl glycidylether, and butyl glycidyl ether. The activator may include one or moreof triethyl borane, trimethyl borane, triisobutylborane, andtriphenylborane. In many embodiments, the activator is triethyl borane.

The initiating system includes an organic cation and an alcohol. Whileany of the organic cations and/or alcohols described herein may be used,in many embodiments, the organic cation is phosphazene and the alcoholis any compound containing more than one hydroxyl group, such as anydiol and/or triol. For example, the alcohol compound may be1,4-dibenzenedimethanol. An example of a general synthetic route for thecopolymerization of epoxide monomer and carbon dioxide using an alcoholcompound/phosphazene initiating system is provided in Scheme 5:

where X is any halide, pseudohalide, alkoxide, phenoxide, carboxylate,carbonate, hydrogen carbonate, etc.; where each of R, R₁, R₂, R₃, R₄ isindependently one or more of any alkyl group including saturated andunsaturated, aromatic, cyclic alkyl group, heteroatom (e.g., halide, N₃,O, S, etc) containing alkyl groups. In other embodiments, any compoundcontaining an active protic hydrogen may be used, including, but notlimited to, one or more alcohols, thiols, phenols, carboxylic acids,etc.

FIG. 4 is a flowchart of a method of making a block copolymer ofpolycarbonate comprising contacting 402 a first epoxide monomer andcarbon dioxide in the presence of an activator including trialkyl boraneand an initiator to form a first polycarbonate block, and adding 404 asecond epoxide monomer to form a second polycarbonate block of a blockcopolymer. In many embodiments, the second polycarbonate block isdifferent from the first polycarbonate block. The method 400 may be usedto form, for example, AB or ABA block copolymers, wherein block A andblock B are different.

Contacting and/or adding may refer to bringing two or more componentsinto proximity, such as physical and/or chemical proximity. In manyembodiments, contacting may include adding and/or mixing two or morecomponents in a reaction vessel and/or charging a chamber including thereaction vessel with a gaseous component sufficient to bring at leasttwo of the components into physical and/or chemical proximity. In manyembodiments, the contacting and adding is generally in the presence ofthe same activator and initiator. In other embodiments, the contactingand adding may be in the presence of a different activator and/or adifferent initiator.

The first epoxide monomer may include one or more of ethylene oxide,propylene oxide, 1-butene oxide, 1-hexene oxide, 1-octene oxide, styreneoxide, cyclohexene oxide, allyl glycidyl ether, and butyl glycidylether.

Any of the activators and initiators described herein may be used. Inmany embodiments, the activator includes a trialkyl borane. For example,the trialkyl borane may include one or more of triethyl borane,trimethyl borane, triisobutylborane, and triphenylborane. In otherembodiments, the activator may include an alkyl borane and/or alkylaluminum. The initiator may include an organic cation and either analkali metal or alcohol compound. The organic cation may include one ormore of phosphazenium, ammonium, and phosphonium. The alkali metal mayinclude one or more of lithium, potassium, and sodium. The alcoholcompound may include any compound containing more than one hydroxylgroup, such as a diol and/or triol. In other embodiments, any compoundcontaining an active protic hydrogen may be used in place of the alcoholcompound.

The second epoxide may include one or more of ethylene oxide, propyleneoxide, 1-butene oxide, 1-hexene oxide, 1-octene oxide, styrene oxide,cyclohexene oxide, allyl glycidyl ether, and butyl glycidyl ether. Inmany embodiments, the second epoxide monomer is different from the firstepoxide monomer. In other embodiments, the first and second epoxidemonomers are the same.

FIG. 5 is a block flow diagram of a method of making a polycarbonate,according to one or more embodiments of this disclosure. One or morecyclic monomers and carbon dioxide are contacted 502 in the presence ofone or more of a Lewis acid activator, an initiator and/or complexinitiator, and an ionic liquid. The one or more cyclic monomers andcarbon dioxide are copolymerized 504 to form a polycarbonate. Thestructure and terminal functionality of the polycarbonate can beadjusted by the initiator, including multifunctional and macromoleculartype. Bifunctional, heterofunctional block copolymers can be createdaccording to an embodiment of this disclosure. In addition,polycarbonates can be formed via anionic alternating copolymerization ofcyclic monomer (e.g., epoxide monomer) and carbon dioxide to formperfectly or nearly perfectly alternating polycarbonates.

The one or more cyclic monomers can include any epoxide monomer. Theepoxide monomer may generally be characterized by the following chemicalstructure:

where each of R₁, R₂, R₃, and R₄ is independently one or more of alkylgroup or containing functional groups such as one or more of halide,vinyl, azide, thiol, ether, ester, ketone, aldehyde, and acid. In manyembodiments, the epoxide monomer may include one or more of propyleneoxide, cyclohexene oxide, ethylene oxide, styrene oxide, and n-butylglycidyl ether. In other embodiments, the one or more cyclic monomerscan include one or more of epoxides, lactides, caprolactones, propyleneoxides (PO), and cyclohexene oxides (CHO). In further other embodiments,the one or more cyclic monomers can include one or more of epoxides,lactides, caprolactones, propylene oxides, cyclohexene oxides, ethyleneoxides, styrene oxides, and glycidyl ethers. For example, the glycidylethers may include n-butyl glycidyl ethers.

The Lewis Acid activator (or activator) can include one or more oftriisobutyl aluminum, triethyl borane, trialkyl aluminum, trimethylborane, triisobutylborane, triphenylborane, trialkyl borane, dialkylzinc, dialkyl magnesium, diethyl zinc, diethyl magnesium, and the esterforms thereof.

The initiator (anionic nucleophile) can include mono- and/orpoly-alcoholic, phenolic, and acidic salts with cations produced throughdeprotonation by different bases, salts, and other lithium saltsadditives. The cations can include one or more of lithium, sodium,potassium, cesium, ammonium, imidazolium, and phosphonium. The bases caninclude, but are not limited to, one or more of imidazolium alkoxide,lithium alkoxide, lithium phenolate, and alkyllithium (includingmacromolecular alkoxide). The salts can include, but are not limited to,one or more of imidazolium halide, lithium, sodium, potassium, halides,ammonium, tetraalkylammonium, tetraalkylphosphonium in halide,hydroxide, carbonate, and carboxylate. Other lithium salts additives caninclude, but are not limited to, one or more of lithium alkoxide,lithium carbonate, lithium phenolate, lithium halide, LiOH, LiCO₃,LiClO₄, LiPF₆, LiBF₄, and lithium bis(trifluoromethane)sulfonamide(Tf²N). The initiator can include one or more of lithium salts,imidazolium salts, and alkoxide salts. The initiator can include one ormore of lithium benzoxide, lithium chloride, lithium bromide, lithiumtriethylene glycoxide, lithium glycoxide, lithium polystyrene,n-heterocyclic carbene, imidazolium chloride, potassium tertbutyloxide,tetrabutylammonium chloride, and benzene alcohol and phosphazene P2. Theinitiator can include deprotonated alkoxide using one or more of carbeneand butyl lithium.

The ionic liquid can include a salt in a liquid state. The ionic liquidcan include one or more of 1-butyl-3-methylimidazoliumhexaflurophosphate (BMIM-PF₆) and trioctylmethylammoniumbis(trifluoromethyl-sulfonyl)imide. The ionic liquid can include one ormore of methylimidazolium and pyridinium ions. The ionic liquid caninclude one or more imidazolium-based ionic liquids with differentcounter ions, including, but not limited to, one or more of3-Methyl-(4-9)-(fluoro)imidazolium Bis Rtrifluoromethyl)sulfonyllimide,1-hexyl-3-methylimidazolium tris(penta fluoro propyl)trifluorophosphate, and 1-pentyl-3-methyl imidazolium tris(nona fluoro butyl)]trifluoro-phosphate. The ionic liquid can include one or moreammonium-based ionic liquids with different counter ions, including, butnot limited to, choline bis(trifluoromethylsulfonyl)imide, tetrabutylammonium docusate, peg-5-cocomonium methylsulphate. The ionic liquid caninclude one or more super-based derived protonic ionic liquids,including, but not limited to, methyl-triaza bicycloundacane (MTBD) andtrifluoroethanol [MTBDH+] [TFE-]. The ionic liquid can include one ormore polyionic liquids, including, but not limited to, one or more ofpoly(1-[(2-methacryloyloxy)ethyl]-3-butylimidazoliums,poly(1-ethyl-3-vinyl-imidazolium) bis(trifluoromethylsulfonyl) imide,N,N-dimetyl-N,N-diallylammonium bis(trifluoromethylsulfonyl) imide, andpoly(diallyldimethylammonium chloride) solution.

Methods of Controlling Polymer Composition

Referring to FIG. 6, a block flow diagram of a method of controlling apolymer composition is shown, according to one or more embodiments ofthis disclosure. One or more cyclic monomers and carbon dioxide arecontacted 602. An amount of one or more of a Lewis acid catalyst, anionic liquid, and an initiator in the presence of the one or more cyclicmonomers and carbon dioxide is adjusted 602, sufficiently to selectivelymodify a resulting polycarbonate. The one or more cyclic monomers andcarbon dioxide are agitated 604 sufficiently to copolymerize and createthe polycarbonate.

Adjusting 602 includes adding an excess, for example. Adjusting can alsoinclude modifying one or more of ratios of catalyst/ionic liquid,catalyst/initiator, activator/cyclic monomers, ionic liquid/cyclicmonomer and initiator/cyclic monomer, polymerization pressure (1 atm to50 atm), and temperature (ambient temperature to 120° C.). In oneexample, ratio of ionic liquid/cyclic monomer is increased to affect thesolubility of carbon dioxide and the resulting carbonate percentage inthe polycarbonate.

Selectively modifying includes one or more of modifying a ratio ofblocks, modifying a gradient, introducing a terminal functional group,copolymerizing with other macromolecular initiates, affecting randomnessof blocks, and altering a structure. Polycarbonates can be modified ortuned according to embodiments of the present invention to create twotypes of block copolymer structures, including a gradient and randomcopolymer with a carbonate composition from about 2% to about 100%, fromabout 5% to about 80%, and from about 10% to about 60%, for example.Selectively modifying includes increasing or decreasing a gradient inthe copolymer, increasing or decreasing randomness of blocks, andincreasing the amount of carbonate in the resulting copolymer, forexample. By choosing appropriate alcohol, phenol, acid, heterofuntionalpolycarbonates, polyol, and block polycarbonate copolymers withpolystyrene, polybutadiene, polyisoprene, poly(ethylene oxide) could beprepared, for example.

In some embodiments, a process of copolymerization of CO₂ and epoxidescatalyzed by trialkyl aluminum or triethyl borane is shown. Thesynthetic process catalyzed by triisobutyl aluminum as an example isshown in scheme 6, initiated by deprotonated alkoxide using carbene orbutyl lithium, or directly by imidazolium salts and lithium salts:

In the examples, three additives are used to tune or modify thecomposition of carbonates. One is the activator Al(iBu)₃, and the othersare ionic liquid, lithium salts and CO₂-philic solvents. Ionic liquidcould be: 1) Imidazolium based ionic liquids with different counter ion,3-Methyl-(4-9)-(fluoro)imidazolium Bis[(trifluoromethyl) sulfonyl]imide,1-hexyl-3-methylimidazolium tris(penta fluoro propyl)trifluoro phosphateand 1-pentyl-3-methyl imidazolium tris(nona fluoro butyl)]trifluoro-phosphate etc.; 2) Ammonium based ionic liquids with differentcounter ions, choline bis(trifluoromethylsulfonyl)imide, tetrabutylammonium docusate, peg-5-cocomonium methylsulphate etc. (ref: J. Phys.Chem. B, Vol. 111, No. 30, 2007); 3) Super based derived protonic ionicliquids, Methyl-triaza bicycloundacane (MTBD) and trifluoroethanol[MTBDH+] [TFE-] etc. (ref: Angew. Chem. Int. Ed. 2010, 49, 5978-5981);B) Polyionic liquids:poly(1-[(2-methacryloyloxy)ethyl]-3-butylimidazoliums,poly(1-ethyl-3-vinyl-imidazolium) bis(trifluoromethylsulfonyl) imide,N,N-dimetyl-N,N-diallylammonium bis(trifluoromethylsulfonyl) imide andpoly(diallyldimethylammonium chloride) solution etc. (Electrochimic aActa, doi: 10.1016/j.electacta.2015.03.038)]. Lithium salts could be:lithium alkoxide, alkyllithium, lithium carbonate, lithium phenolate,lithium halide, LiOH, LiCO3, LiClO4, LiPF6, LiBF4, lithiumbis(trifluoromethane)sulfonamide (Tf2N), etc. CO₂-philic solvents couldbe: THF, poly(ethylene glycol) dimethyl ether, polypropyleneglycoldimethylether, polydimethyl siloxane, etc (M. B. Miller, D. R. Luebke,R. M. Enick, Energy & Fuels 2010, 24, 6214-6219). Through differentfeeding ratios, different mean compositions and terminal functionalityof polycarbonates and block copolymers initiated by othermacromolecualar polyols (hydroxyl terminated polystyrene (PSt),polyisoprene (PI), polybutadiene (PI), poly(ethylene oxide) (PEO), forexample) can be achieved. Not only the sequential polymerization ofother cyclic monomers, such as lactide, caprolactone leading blockcopolymers, but also the copolymerization of the latter monomers withCO₂ can be contemplated.

EXAMPLE 1

A 300 mL Parr reactor equipped with stirrer was first dried in an ovenat 120° C. overnight, then immediately placed into the side glove boxchamber. After keeping it under vacuum for one hour, the reaction vesselwas moved into the main glove box with argon atmosphere. Thecopolymerization of CO₂ with CHO described below is taken from entry 11in Table 1 as an example. n-Butyllithium (n-BuLi, 21.6 μL, 0.034 mmol)was firstly added into the reactor, then, phosphazene base (P₄-t-Bu,34.6 μL, 0.034 mmol) was added, followed by the addition of triethylborane (70 μL, 0.069 mmol). Cyclohexene oxide (CHO, 7 mL, 69 mmol) wasfinally added. The reactor was sealed and taken out from the glove boxand charged with CO₂ under a pressure of 30 bars. The copolymerizationwas carried out at 70° C. for 12 hr. At the end of the polymerization,the unreacted CO₂ was released, and the solid product was removed. Asmall fraction of the crude product was dissolved in CHCl₃, precipitatedin methanol, filtered and dried, for characterization. Thecopolymerization of other epoxides with CO₂ was carried out in similarprocesses. The results are listed in Table 1.

The analysis by Gel Permeation Chromatography (GPC), MALDI-TOF massspectroscopy, Infrared Spectroscopy (IR) and Nuclear Magnetic ResonanceSpectroscopy (NMR) were used to provide useful information of the systemin order to prove the polycarbonate structure. All samples,characterized by GPC, exhibited monomodal and narrow molecular weightdistribution (M_(w)/M_(n)<1.3) and expected molecular weights (FIGS.7-11). Moreover, these results confirm the livingness of thecopolymerization initiated by the system described in this patent. Thecarbonate content/alternating structure, precisely determined by ¹H NMRcharacterization, revealed the high carbonate content of the samples(FIGS. 12-16, Table 1). In addition, MALDI-TOF characterization clearlyshows the formation of one main population of perfectly alternating(100%) poly (cyclohexene carbonates) (FIG. 17). IR spectroscopy supportsthese results showing a strong polycarbonate peak at 1750 cm⁻¹¹. IRanalysis also shows that selectivity of the copolymerization of CHO withCO₂ is 100% for linear polymer with practically absence of cyclicspecies (FIG. 18).

EXAMPLE 2

Representative procedure of copolymerization of CO₂ and epoxideinitiated with phosphazenium lithium salts: Take CHO from entry 11 inTable 1 as an example. A 300 mL Parr reactor equipped with mechanicalstirrer was first dried in an oven at 120° C. overnight, thenimmediately placed into the glove box chamber. After keeping it undervacuum for one hour, the reaction vessel was moved into the glove boxunder argon atmosphere. n-Butyllithium (n-BuLi, 21.6 μL, 0.034 mmol) wasfirstly added into the reactor, then, phosphazene base (P4-t-Bu, 34.6μL, 0.034 mmol) was added, followed by the addition of triethyl borane(70 μL, 0.069 mmol). Cyclohexene oxide (CHO, 7 mL, 69 mmol) was finallyadded. The reactor was sealed and taken out from the glove box andcharged with CO₂ under a pressure of 10 bars. The copolymerization wascarried out at 70° C. for 12 hr. At the end of the polymerization, theunreacted CO₂ was released, and the solid product was removed. A smallfraction of the crude product was dissolved in CHCl3, precipitated inmethanol, filtered and dried, for characterization. See FIGS. 19-20.

TABLE 1 Copolymerization results of selected different epoxides with CO₂activated by TEB initiated with phosphazenium lithium salts:[Initiator]/ DP Yields^(c) PC^(d) Selectivity Mn(×10³)/ Entry M^(a)Initiators^(b) [TEB] Temp. targeted (%) mol % %^(d) PDI^(e) 1 EO n-BuLi/1/1 r.t. 200 79 70 97 12.0/12 t-BuP₄ 2 EO n-BuLi/ 1/1 r.t. 500 80 77 9737.0/1.2 t-BuP₄ 3 EO n-BuLi/ 1/1 r.t. 600 52 74 98 29.0/1.3 t-BuP₄ 4 POn-BuLi/ 1/2 60 1000 80 96 95 75.0/1.1 t-BuP₄ 5 PO n-BuLi/ 1/2 60 1000 8095 81 47.0/1.2 t-BuP₂ 6 PO PI-b-PStOLi 1/2 60 1000 60 99 95 65.0/1.1(8.0K)/t-BuP₄ 7 SO n-BuLi/ 1/8 60 200 80 99 81 15.0/1.1 t-BuP₄ 8 CHOn-BuLi/ 1/2 70 75 95 99 99  9.2/1.1 t-BuP₄ 9 CHO n-BuLi/ 1/2 70 500 8799 99 73.0/1.2 t-BuP₄ 10 CHO n-BuLi/ 1/2 70 1000 90 99 99  120/1.3t-BuP₄ 11 CHO n-BuLi/ 1/2 70 2000 90 99 99  284/1.3 t-BuP₄ 12 CHOPStOLi(4.0K)/ 1/2 70 200 73 99 99 24.0/1.1 t-BuP₄ 13 CHO PStOLi(4.0K)/1/2 70 1000 87 99 99  100/1.1 t-BuP₄ 14 CHO PI-b-PStOLi 1/2 70 1000 8099 99 95.0/1.1 (8.0K)/t-BuP₄ 15 BGE n-BuLi/ 1/2 60 200 78 71 73 10.0/1.1t-BuP₂ ^(a)EO: ethylene oxide; PO: propylene oxide; CHO: cyclohexeneoxide; BGE: butyl glycidyl ether. ^(b)t-BuP₄, t-BuP₂: phosphazene base;PSt: polystyrene; PI: polyisoprene. ^(c)Calculated by gravity. ^(d)PC:polycarbonate contents; calculated based on ¹H NMR of reaction mixture.^(e)Determined by GPC using tetrahydrofuran as the fluent andpolystyrene as standard.

EXAMPLE 3

Representative procedure of copolymerization of CO₂ with ethylene oxide(EO): Take Entry 2 in Table 2 as an example. A 50 mL Parr reactor withmagnetic stirrer and a small glass vial inside was first dried in anoven at 120° C. overnight, then immediately placed into the glove boxchamber. After keeping under vacuum for 2-3 hours, the reaction vesselwas moved into the glove box under argon atmosphere. 110 mg (0.08 mmol)of 1,4-benzyldimethanol (BDM) in 1.5 mL of THF was first added into thereactor, then equal equivalent of t-BuP4 solution (0.16 mmol) was slowlyadded accompanying with the generation of white precipitate.triethylborane in THF solution (0.16 mmol) was dropped into thissuspension solution. The white precipitates dissolved gradually, and atransparent solution was formed. Ethylene oxide (EO, 2 mL, 40 mmol) wascarefully added into the glass vial which was placed on the bottom ofthe reactor. The reactor was quickly sealed, taken out from the glovebox and charged with CO₂ to a pressure of 10 bar. After the whole systemwas kept for 20 min, the vial was turned over through vigorous shakingof reactor to release the monomer E0 and mix with other reactants in thereactor. The copolymerization was carried out at room temperature for 10hr., the unreacted CO₂ was slowly released, and the polymer solution wasquenched with HCl in methanol (1 mol/L). The crude product was dilutedwith CH₂Cl₂ and then precipitated in cold methanol. The product wascollected by centrifugation and dried in vacuum at room temperatureuntil constant weight. See FIGS. 21A-21B.

TABLE 2 Copolymerization results of selected different epoxides with CO₂activated by TEB under metal free conditions [Initiator]/ DP Yields^(c)PC^(d) Selectivity Mn(×10³)/ Entry M^(a) Initiators^(b) [TEB] Temp.targeted (%) mol % %^(d) PDI^(e)  1^(f) EO BDM + 1/0.5 r.t. 500 40 99 9918.0/1.1   t-BuP₄  2^(f) EO BDM + 1/1 r.t. 500 66 99 97 29.0/1.1  t-BuP₄  3^(f) EO BDM + 1/2 r.t. 500 86 49 96 21.0/1.1   t-BuP₄  4^(f) EOBDM + 1/1 40 500 74 99 92 33.0/1.1   t-BuP₄  5^(f) EO NOct₄Cl 1/1 r.t.500 35 99 99  7.4/1.6  6^(f) EO PPNCl 1/1 r.t. 500 87 56 98 24.0/1.4  7PO BDM + 1/2 50 1000 77 98 98 32.0/1.2   t-BuP₄  8 PO BDM + 1/2 60 100085 99 97 35.0/1.1   t-BuP₄  9 PO BDM + 1/2 60 1000 83 98 98 45.0/1.2  t-BuP₄ 10 PO BDM + 1/2 70 1000 69 96 62 22.0/1.1 t-BuP₄ 11 PO BDM + 1/280 1000 54 97 53 18.0/1.1 t-BuP₄ 12 PO NBu₄Cl 1/2 60 1000 46 95 9750.0/1.2 13 BO BDM + 1/2 60 500 87 97 99 31.0/1.1 t-BuP₄ 14 BO BDM + 1/260 1000 84 98 98 28.0/1.2 t-BuP₄ 15 BO PPNCl 1/2 60 500 83 96 9829.0/1.2 16 HO BDM + 1/2 50 1000 72 99 98 63.0/1.1 t-BuP₄ 17 HO BDM +1/2 60 1000 74 98 97 69.0/1.1 t-BuP₄ 18 HO PPNCl 1/2 60 500 65 97 9832.0/1.1 19 OO BDM + 1/2 50 1000 72 97 98 70.0/1.1 t-BuP₄ 20 OO BDM +1/2 60 1000 73 99 98 73.0/1.1 t-BuP₄ 21 OO PPNCl 1/2 60 500 70 97 9941.0/1.2 22^(g) SO BnOH + 1/2 60 100 45 95 57  5.1/1.2 t-BuP₄ 23^(g) SOBnOH + 1/2 60 200 42 94 53  8.9/1.1 t-BuP₄   24^(g) SO BnOH + 1/2 60 50014 95 43  9.1/1.1 t-BuP₄   25^(g) SO BnOH + 1/4 60 500 16 93 61  9.7/1.1t-BuP₄ 26^(g) SO PPNCl 1/8 60 500 67 99 85 15.0/1.1 27 CHO BnOH + 1/2 80250 88 99 97 24.0/1.2 t-BuP₄ 28 CHO PPNCI 1/2 80 4000 90 99 95 76.4/1.229 AGE BDM + 1/2 50 1000 78 94 97 46.0/1.1 t-BuP₄ 30 AGE BDM + 1/2 601000 68 93 96 63.0/1.1 t-BuP₄ 31 AGE PPNCI 1/2 60 500 56 86 97 12.0/1.132 BGE BDM + 1/2 60 100 45 92 63  4.1/1.1 t-BuP₄   33 BGE BDM + 1/2 60500 36 87 42  5.3/1.2 t-BuP₄ ^(a)EO: ethylene oxide; PO: propyleneoxide; CHO: cyclohexene oxide; BO: 1-butene oxide; HO: 1-hexene oxide;OO: 1-octene oxide; SO: styrene oxide; AGE: allyl glycidyl ether; BGE:butyl glycidyl ether. ^(b)BDM: 1,4-benzenedimethanol; BnOH: benzylalcohol; PPNCl: bis (triphenylphosphoranylidene) ammonium chloride;NOct₄Cl: tetraoctylammonium chloride; NBu₄Cl: tetrabutylammoniumchloride; t-BuP₄: phosphazene base. ^(c)Calculated by gravity. ^(d)PC:polycarbonate contents; calculated based on ¹H NMR of reaction mixture.^(e)Determined by GPC using tetrahydrofuran as the fluent andpolystyrene as standard. ^(f)Determined by GPC using dimethylformamideas the fluent and polystyrene as standard. ^(g)Determined by GPC usingchloroform as the fluent and polystyrene as standard.

EXAMPLE 4

Representative procedure of copolymerization of CO₂ with propylene oxide(PO): Take Entry 7 in Table 2 as an example. A 50 mL Parr reactor withmagnetic stirrer was first dried in an oven at 120° C. overnight, thenimmediately placed into the glove box chamber. After keeping undervacuum for 2-3 hours, the reaction vessel was moved into the glove boxunder argon atmosphere. 3.9 mg (0.029 mmol) of BDM in 1.0 mL of THF wasfirst added into the reactor, then equal equivalent of t-BuP4 solution(0.058 mmol) was slowly added accompanying with the generation of whiteprecipitate. triethylborane in THF solution (0.116 mmol) was droppedinto this suspension solution. The white precipitates dissolvedgradually, and a transparent yellow solution was formed. After propyleneoxide (PO, 2 mL, 29 mmol) was added into the reactor, and the autoclavewas quickly sealed, taken out from the glove box and charged with CO₂ toa pressure of 10 bar. The copolymerization was carried out at 60° C. for10 hr. At the end of the polymerization, the unreacted CO₂ was slowlyreleased, and the polymer solution was quenched with HCl in methanol (1mol/L). The crude product was diluted with CH₂Cl₂ and then precipitatedin cold methanol. The product was collected by centrifugation and driedin vacuum at room temperature until constant weight. See FIGS. 22A-22B.

EXAMPLE 5

Representative procedure of copolymerization of CO₂ with 1-butene oxide(BO): Take Entry 14 in Table 2 as the example. A 50 mL Parr reactor withmagnetic stirrer was first dried in an oven at 120° C. overnight, thenimmediately placed into the glove box chamber. After keeping undervacuum for 2-3 hours, the reaction vessel was moved into the glove boxunder argon atmosphere. 3.2 mg (0.023 mmol) of BDM in 1.0 mL of THF wasfirst added into the reactor, then equal equivalent of t-BuP4 solution(0.046 mmol) was slowly added accompanying with the generation of whiteprecipitate. triethylborane in THF solution (0.092 mmol) was droppedinto this suspension solution. The white precipitates dissolvedgradually, and a transparent yellow solution was formed. After 1-buteneoxide (BO, 2 mL, 23 mmol) was added into the reactor, and the autoclavewas quickly sealed, taken out from the glove box and charged with CO₂ toa pressure of 10 bar. The copolymerization was carried out at 60° C. for10 hr. At the end of the polymerization, the unreacted CO₂ was slowlyreleased, and the polymer solution was quenched with HCl in methanol (1mol/L). The crude product was diluted with CH₂Cl₂ and then precipitatedin cold methanol. The product was collected by centrifugation and driedin vacuum at room temperature until constant weight. See FIGS. 23-24.

EXAMPLE 6

Representative procedure of copolymerization of CO₂ with 1-hexene oxide(HO): Take Entry 16 in Table 2 as the example. A 50 mL Parr reactor withmagnetic stirrer was first dried in an oven at 120° C. overnight, thenimmediately placed into the glove box chamber. After keeping undervacuum for 2-3 hours, the reaction vessel was moved into the glove boxunder argon atmosphere. 2.3 mg (0.017 mmol) of BDM in 1.0 mL of THF wasfirst added into the reactor, then equal equivalent of t-BuP4 solution(0.034 mmol) was slowly added accompanying with the generation of whiteprecipitate. triethylborane in THF solution (0.068 mmol) was droppedinto this suspension solution. The white precipitates dissolvedgradually, and a transparent yellow solution was formed. After 1-hexeneoxide (HO, 2 mL, 16.6 mmol) was added into the reactor, and theautoclave was quickly sealed, taken out from the glove box and chargedwith CO₂ to a pressure of 10 bar. The copolymerization was carried outat 60° C. for 10 hr. At the end of the polymerization, the unreacted CO₂was slowly released, and the polymer solution was quenched with HCl inmethanol (1 mol/L). The crude product was diluted with CH₂Cl₂ and thenprecipitated in cold methanol. The product was collected bycentrifugation and dried in vacuum at room temperature until constantweight. See FIGS. 25-26.

EXAMPLE 7

Representative procedure of copolymerization of CO₂ with 1-octene oxide(OO): Take Entry 20 in Table 2 as the example. A 50 mL Parr reactor withmagnetic stirrer was first dried in an oven at 120° C. overnight, thenimmediately placed into the glove box chamber. After keeping undervacuum for 2-3 hours, the reaction vessel was moved into the glove boxunder argon atmosphere. 1.8 mg (0.013 mmol) of BDM in 1.0 mL of THF wasfirst added into the reactor, then equal equivalent of t-BuP4 solution(0.026 mmol) was slowly added accompanying with the generation of whiteprecipitate. triethylborane in THF solution (0.052 mmol) was droppedinto this suspension solution. The white precipitates dissolvedgradually, and a transparent yellow solution was formed. After 1-octeneoxide (OO, 2 mL, 13.4 mmol) was added into the reactor, and theautoclave was quickly sealed, taken out from the glove box and chargedwith CO₂ to a pressure of 10 bar. The copolymerization was carried outat 60° C. for 10 hr. At the end of the polymerization, the unreacted CO₂was slowly released, and the polymer solution was quenched with HCl inmethanol (1 mol/L). The crude product was diluted with CH₂Cl₂ and thenprecipitated in cold methanol. The product was collected bycentrifugation and dried in vacuum at room temperature until constantweight. See FIGS. 27-28.

EXAMPLE 8

Representative procedure of copolymerization of CO₂ with styrene oxide(SO): Take Entry 26 in Table 2 as the example. A 50 mL Parr reactor withmagnetic stirrer was first dried in an oven at 120° C. overnight, thenimmediately placed into the glove box chamber. After keeping undervacuum for 2-3 hours, the reaction vessel was moved into the glove boxunder argon atmosphere. 20 mg (0.035 mmol) of PPNC1 in 1.0 mL of THF wasfirst added into the reactor, then triethylborane in THF solution (0.28mmol) was dropped into this suspension solution. Styrene oxide (SO, 2mL, 17.5 mmol) was added into the reactor, and the autoclave was quicklysealed, taken out from the glove box and charged with CO₂ to a pressureof 10 bar. The copolymerization was carried out at 60° C. for 10 hr. Atthe end of the polymerization, the unreacted CO₂ was slowly released,and the polymer solution was quenched with HCl in methanol (1 mol/L).The crude product was diluted with CH₂Cl₂ and then precipitated in coldmethanol. The product was collected by centrifugation and dried invacuum at room temperature until constant weight. See FIGS. 29-30.

EXAMPLE 9

Representative procedure of copolymerization of CO₂ with cyclohexeneoxide (CHO): Take Entry 28 in Table 2 as the example. A 50 mL Parrreactor with magnetic stirrer was first dried in an oven at 120° C.overnight, then immediately placed into the glove box chamber. Afterkeeping under vacuum for 2-3 hours, the reaction vessel was moved intothe glove box under argon atmosphere. 11 mg (0.040 mmol) of NBu4Cl in1.0 mL of THF was first added into the reactor, then triethylborane inTHF solution (0.080 mmol) was dropped into this suspension solution. CHO(2 mL, 20.0 mmol) was added into the reactor, and the autoclave wasquickly sealed, taken out from the glove box and charged with CO₂ to apressure of 10 bar. The copolymerization was carried out at 60° C. for10 hr. At the end of the polymerization, the unreacted CO₂ was slowlyreleased, and the polymer solution was quenched with HCl in methanol (1mol/L). The crude product was diluted with CH₂Cl₂ and then precipitatedin cold methanol. The product was collected by centrifugation and driedin vacuum at room temperature until constant weight. See FIGS. 31-32.

EXAMPLE 10

Representative procedure of copolymerization of CO₂ with allyl glycidylether (AGE): Take Entry 29 in Table 2 as the example. A 50 mL Parrreactor with magnetic stirrer was first dried in an oven at 120° C.overnight, then immediately placed into the glove box chamber. Afterkeeping under vacuum for 2-3 hours, the reaction vessel was moved intothe glove box under argon atmosphere. 2.3 mg (0.017 mmol) of BDM in 1.0mL of THF was first added into the reactor, then equal equivalent oft-BuP4 solution (0.034 mmol) was slowly added accompanying with thegeneration of white precipitate. triethylborane in THF solution (0.068mmol) was dropped into this suspension solution. The white precipitatesdissolved gradually, and a transparent yellow solution was formed. AfterAGE (2 mL, 16.8 mmol) was added into the reactor, and the autoclave wasquickly sealed, taken out from the glove box and charged with CO₂ to apressure of 10 bar. The copolymerization was carried out at 60° C. for10 hr. At the end of the polymerization, the unreacted CO₂ was slowlyreleased, and the polymer solution was quenched with HCl in methanol (1mol/L). The crude product was diluted with CH₂Cl₂ and then precipitatedin cold methanol. The product was collected by centrifugation and driedin vacuum at room temperature until constant weight. See FIGS. 33-34.

EXAMPLE 11

Representative procedure of copolymerization of CO₂ with butyl glycidylether (BGE): Take Entry 32 in Table 2 as the example. A 50 mL Parrreactor with magnetic stirrer was first dried in an oven at 120° C.overnight, then immediately placed into the glove box chamber. Afterkeeping under vacuum for 2-3 hours, the reaction vessel was moved intothe glove box under argon atmosphere. 19 mg (0.14 mmol) of BDM in 1.0 mLof THF was first added into the reactor, then equal equivalent of t-BuP4solution (0.28 mmol) was slowly added accompanying with the generationof white precipitate. triethylborane in THF solution (0.056 mmol) wasdropped into this suspension solution. The white precipitates dissolvedgradually, and a transparent yellow solution was formed. After BGE (2mL, 14 mmol) was added into the reactor, and the autoclave was quicklysealed, taken out from the glove box and charged with CO₂ to a pressureof 10 bar. The copolymerization was carried out at 60° C. for 10 hr. Atthe end of the polymerization, the unreacted CO₂ was slowly released,and the polymer solution was quenched with HCl in methanol (1 mol/L).The crude product was diluted with CH₂Cl₂ and then precipitated in coldmethanol. The product was collected by centrifugation and dried invacuum at room temperature until constant weight. See FIGS. 35-36.

EXAMPLE 12

Representative procedure of sequential copolymerization of CO₂ with1-hexene oxide (HO) and cyclohexene oxide (CHO): Take Entry 4 in Table 3as the example. A 300 mL Parr reactor with mechanical stirrer was firstdried in an oven at 120° C. overnight, then immediately placed into theglove box chamber. After keeping under vacuum for 2-3 hours, thereaction vessel was moved into the glove box under argon atmosphere. 17mg (0.12 mmol) of BDM in 3.0 mL of THF was first added into the reactor,then equal equivalent of t-BuP4 solution (0.24 mmol) was slowly addedaccompanying with the generation of white precipitate. triethylborane inTHF solution (0.5 mmol) was dropped into this suspension solution. Thewhite precipitates dissolved gradually, and a transparent yellowsolution was formed. After 1-hexene oxide (HO, 15 mL, 124 mmol) wasadded into the reactor, and the autoclave was quickly sealed, taken outfrom the glove box and charged with CO₂ to a pressure of 10 bar. Thecopolymerization was carried out at 50° C. for 10 hr., the unreacted CO₂and HO was removed under short vacuum. CHO (4.2 ml, 41.6 mmol) in 8 mLof THF was quickly added by syringe. The reactor was charged CO₂ againto 10 bar, and polymerization extended for another 10 hrs. At the end ofthe polymerization, the unreacted CO₂ was slowly released. The crudeproduct was dissolved in some amount of CH₂Cl₂ and then precipitated incold methanol. The product was collected by centrifugation and dried invacuum at room temperature until constant weight. See FIGS. 37-38.

TABLE 3 Related data of polycarbonate triblock copolymer synthesisthrough sequential addition of epoxide monomers initiated with1,4-benzenedimethanol/P4.^(a) Feed Ratio Conv.^(b) Conv.^(b)Selectivity.^(b) Mn/ [PHC]/ Entry [HO]/[CHO] [HO]% [CHO]% % PDI^(d)[PCHC]^(c) 0 10/0 80 — 98 59.0/1.1 — 1  9/1 77 85 97 83.0/1.0 8.5/1.0 2 7/1 78 87 98 65.0/1.2 6.3/1.0 3  5/1 82 92 97 69.0/1.2 4.2/1.0 4  3/179 91 99 73.0/1.1 2.6/1.0 ^(a)The copolymerization was carried out insame reactor at 50° C. for HO and 60° C. for CHO respectively.^(b)Determined by ¹H NMR of crude products. ^(c)[PHC]/[PCHC]: molarratio of poly (hexene carbonate) and poly (cyclohexene carbonate) inobtained triblock copolymer based on 1H NMR data. ^(d)Determined by GPCusing tetrahydrofuran as the fluent and polystyrene as standard.

EXAMPLE 13

A representative procedure of CO₂ copolymerization of propylene oxidewith carbene catalyzed by triisobutyl aluminum was performed. Inside aglove box under argon, to a pre-dried 50 mL of autoclave fitted withmagnetic stirring bar, 10.8 mg of 2-phenyl ethanol (86 μmol) was addedfollowed by 1.5 mL of toluene. 1,3-diisopropylimidazol-2-ylidene intoluene (86 μmol) was added to deprotonate the alcohol. Ten minuteslater, 246 mg of ionic liquid (10 eq.), 1-butyl-3-methylimidazoliumhexaflurophosphate and triisobutyl aluminum in toluene (103 μmol) wereadded into the autoclave. To prevent homopolymerization before chargingCO₂, 1.5 mL of propylene oxide was charged into a separate small vialwhich was put inside the autoclave. CO₂ was charged into the sealedautoclave to 10 bar. Then, copolymerization was carried out undervigorous stirring at room temperature. After the reaction time, thecarbon dioxide slowly vented, and the reaction quenched with drops of10% HCl. Toluene was used to extract the polymer to remove the addedionic liquid. The organic solution was concentrated and dried forcharacterization. The results were listed in Table 4. The obtainedpolycarbonates (non-quenched polymer crude mixture) exhibiteddegradation phenomena characterized by IR (See FIG. 39A illustrating agraphical view of an IR degradation characterization of a preparedpolymer initiated by N-heterocyclic carbene (NHC), according to one ormore embodiments of this disclosure), GPC (See FIG. 39B illustrating agraphical view of a gel permeation chromatography (GPC) degradationcharacterization of a prepared polymer initiated by N-heterocycliccarbene (NHC), according to one or more embodiments of this disclosure),suggesting their gradient structure.

TABLE 4 Gradient poly(ether carbonate) copolymer initiated by carbenesystem iBu3Al IL CO2 Conv. PC Selectivity GPC EXP* Initiator (1.0) (Eq.)(Eq.) solvent PO (atm) Temp. time (% PO) (mol %) (%) (×10³) 1 PhEOH/NHC0 0 Tol 7.2M 10 60 0  0 2 PhEOH/NHC 1.0 0 Tol 7.2M 10 60 3 ds 51 26 301.39/2.28 3 PhEOH/NHC 1.5 0 Tol 7.2M 10 R.t. 16 + 10(40° C.) 91 1.1 6414.7/1.18 4 PhEOH/NHC 1.2 5 Tol 7.2M 10 R.t. 16 + 8(40° C.) 12 42 731.57/1.37 5 PhEOH/NHC 1.5 10 Tol 7.2M 10 R.t. 16 26 27 85 6.46/1.10 6PhEOH/NHC 1.2 20 Tol 7.2M 10 R.t. 3 ds 36 50 99.3 5.82/1.16 7 PhEOH/NHC1.2 5 Tol. 7.2M 10 r.t. 16 h 2.5 51 >99% 8 PhEOH/NHC 1.2 8 Tol. 7.2M 10r.t. 16 h 4.9 58   93% 9 PhEOH/NHC 1.2 10 Tol. 7.2M 10 r.t. 16 h 6.954 >99% 11 PhEOH/NHC 1.2 20 Tol. 7.2M 10 r.t. 16 h 10.3 38   99% 12PhEOH/NHC 5.0 10 Tol. 7.2M 10 r.t. 16 h 26.2 37   97% 13 PhEOH/NHC 3.010 Tol. 7.2M 10 r.t. 16 h 19.3 42   97% 14 PhEOH/NHC 2.0 10 Tol. 7.2M 10r.t. 16 h 9.9 46   97% 15 Acetic acid/ 1.2 10 Tol. 7.2M 10 r.t. 16 h 3.548   99% NHC    16 PhEOH/NHC 1.2 10 DCM 7.2M 10 r.t. 16 h 0.8 53   98%17 PhEOH/NHC 1.2 10 Dioxane 7.2M 10 r.t. 16 h 5.8 50   98% 18 PhEOH/NHC1.2 10 THF 7.2M 10 r.t. 16 h 9.3 44 >99% 19 PhEOH/NHC 1.2 10 Cyclic 7.2M10 r.t. 16 h Trace 52 carbonate 20 PhEOH/NHC 1.2 10 hexane 7.2M 10 r.t.16 h 6.4 45   97% 21 PhEOH/NHC 2.0 10 Tol. 5.6M 10 r.t. 16 h 84.033 >99% [00150] 22 PhEOH/NHC 1.2 10 Tol. 5.6M 30 r.t. 16 h 10.0 16 >99%[00151] *: Exp. 1-20, propylene oxide as monomer, 21-22, cyclohexeneoxide as monomer.

EXAMPLE 14

A representative procedure of CO₂ copolymerization of propylene oxidewith imidazolium salt catalyzed by triisobutyl aluminum was performed.Inside a glove box under argon, to a pre-dried 50 mL of autoclave fittedwith magnetic stirring bar, 16 mg of 1,3-diisopropylimidazolium chloride(86 μmol) was added followed by 0.3 g of propylene carbonate. After theimidazolium salt was completely dissolved, 123 mg of ionic liquid (5eq.), 1-butyl-3-methylimidazolium hexaflurophosphate and triisobutylaluminum in toluene (103 μmol) were added into the autoclave. To preventhomopolymerization before charging CO₂, 1.5 mL of propylene oxide wascharged into a separate small vial which was put inside the autoclave.CO₂ was charged into the sealed autoclave to 10 bar. Then,copolymerization was carried out under stirring at 60° C. after thepropylene oxide was mixed through vigorous shaking. After the reactiontime, the carbon dioxide was slowly vented, and quenched the reactionwith drops of 10% HCl. The reaction mixture was precipitated into excessof water to remove propylene carbonate. Toluene was used to extract theprecipitate to remove the added ionic liquid. The organic solution wasconcentrated and dried for characterization. The results were listed inTable 5. The obtained polycarbonates (non-quenched polymer crudemixture) did not exhibit degradation phenomena characterized by IR (seeFIG. 40 illustrating a graphical view of an infrared (IR) degradationtest of prepared polymer initiated by imidazolium chloride, according toone or more embodiments of this disclosure).

TABLE 5 Random poly(propylene carbonate) copolymer initiated byimidazolium chloride Initiator iBu3Al IL CO2 Conv. PPC Selectivity GPCEXP (1.0) (Eq.) (Eq.) solvent PO (atm) Temp. time (% PO) (mol %) (%)(×10³) 23 Pr2lmCl 1.2 5 CPC 12.3M 10 60 16 90 33 nd 2.55/1.28 24 Pr2lmCl1.2 20 CPC 12.3M 10 60 16 56 36 nd 4.67/1.59 25 Pr2lmCl 1.2 0 CPC 13.6M15 60 3 ds 42 nd 22.0/1.12 26 Pr2lmCl 1.1 5 CPC 12.3M 10 60 16 77 34 nd6.48/1.58

EXAMPLE 15

A representative procedure of CO₂ copolymerization of cyclohexene oxidewith lithium salts catalyzed by triisobutyl aluminum was performed.Inside a glove box under argon, to a pre-dried 50 mL of autoclave fittedwith magnetic stirring bar, 93 mg of 2-phenyl ethanol (0.74 mmol) wasadded followed by 1.5 mL of THF. Butyllithium in toluene (0.74 mmol) wasadded to deprotonate the alcohol. Ten minutes later, triisobutylaluminum in toluene (0.20 mmol) were added into the autoclave. Toprevent homopolymerization before charging CO₂, 1.5 mL of cyclohexeneoxide was charged into a separate small vial which was put inside theautoclave. CO₂ was charged into the sealed autoclave to 10 bar. Then,copolymerization was carried out under vigorous stirring at 80° C. Afterthe reaction time, the carbon dioxide slowly vented, and the reactionquenched with drops of 10% HCl. Dichloromathane was used to extract thepolymer. The organic solution was concentrated and precipitated inmethanol. The results were listed in Table 6, FIG. 41-48.

TABLE 6 polycarbonate initiated by lithium salts Li salt InitiatoriBu3Al additive CO2 Yield PC Selectivity GPC EXP (mol/L) (mol/L) (Eq.)solvent Epoxide (atm) Temp. time (%) (mol %) (%) (×10³) 27 BzOLi(0.25)0.066 0 THF CHO(5.0M) 10 80 16 84 99 >99 3.4/1.10 24 BzOLi(0.10) 0.025 0Tol CHO(5.0M) 10 80 16 11 25 >99 2.0/1.20 25 BzOLi(0.10) 0.025 0 THFCHO(5.0M) 10 60 16 13 91 >99 5.3/1.10 26 BzOLi(0.10) 0.066 0 THFCHO(5.0M) 10 60 16 73 88 >99 4.0/1.10 27 BzOLi(0.10) 0.10 0 THFCHO(5.0M) 10 60 16 78 29 >99 5.3/1.10 28 BzOLi(0.10) 0.066 CF₃SO₃Li(1.5)THF CHO(5.0M) 10 80 16 50 12 >99 1.2/1.30 29 BzOLi(0.10) 0.066 LiF(1.5)THF CHO(5.0M) 10 80 16 47 60 >99 1.4/1.40 30 LiCl(0.25) 0.066 0 THFCHO(5.0M) 10 80 16 86 99 >99 2.4/1.10 31 LiBr(0.25) 0.066 0 THFCHO(5.0M) 10 60 16 92 99 >99 2.1/1.10 32 LiO(EO)₃Li 0.13 0 THF CHO(5.0M)10 60 16 91 88 >99 4.1/1.20 (0.25) 33 LiO(EO)₁₄Li 0.13 0 THF CHO(5.0M)10 60 16 97 99 >99 3.0/1.20 (0.25) 34 PSt- 0.066 0 THF CHO(5.0M) 10 6016 90 95 >99 4.1/1.10 CH2CH2OLi (0.25) 35 LiO(EO)₃Li 0.094 0 THFPO(7.2M) 10 r.t. 16 25 61 94 1.8/1.08 (0.18)

EXAMPLE 16

A representative procedure of CO₂ copolymerization of cyclohexene oxidewith macromolecular lithium salts catalyzed by triisobutyl aluminum wasperformed. Inside a glove box under argon, to a pre-dried 50 mL ofautoclave fitted with magnetic stirring bar, 93 mg of 2-phenyl ethanol(0.74 mmol) was added followed by 1.5 mL of THF. Butyllithium in toluene(0.74 mmol) was added to deprotonate the alcohol. Ten minutes later,triisobutyl aluminum in toluene (0.20 mmol) were added into theautoclave. To prevent homopolymerization before charging CO₂, 1.5 mL ofcyclohexene oxide was charged into a separate small vial which was putinside the autoclave. CO₂ was charged into the sealed autoclave to 10bar. Then, copolymerization was carried out under vigorous stirring at80° C. After the reaction time, the carbon dioxide slowly vented, andthe reaction quenched with drops of 10% HCl. Dichloromathane was used toextract the polymer. The organic solution was concentrated andprecipitated in methanol. The results were listed in Table 6, FIG. 49,50.

TABLE 7 Supplementary data of copolymerization of CO₂ and epoxide in thepresence of boron Lewis acids. Initiator Et₃B CO2 Yield PC SelectivityGPC EXP (mol/L) (mol/L) solvent Epoxide (atm) Temp. time (%) (mol %) (%)(×10³) 27 t-BuOK 0.56 — PO, 10 60 16 h 93 94 97  5.10/1.10 (0.28) bulk  28 (Bu)₄NCl 0.28 — PO, 10 60 16 h 85 82 95  9.00/1.10 (0.14) bulk   29(Bu)₄NCl 0.056 — PO, 10 60 16 h 80 73 94  43.0/1.10 (0.028) bulk   30(Bu)₄NCl 0.028 — PO, 10 60 16 h 59 83 78  40.0/1.10 (0.014) bulk   31(Bu)₄NCl 0.056 toluene PO, 10 60 16 h 62 73 85  33.0/1.20 (0.028) 7.2M  32 BnOH/P2 0.014 THF PO, 10 60 16 h 93 88 96  11.0/1.20 (0.07) 7.2M   33BnOH/P4 0.28 THF PO, 10 60 16 h 95 85 95  8.60/1.10 0.14) 7.2M 34 t-BuOK0.13 THF CHO, 10 80 16 h 93 >99 >99% 12.0K/1.07 (0.067) 5.0M

EXAMPLE 17

A representative procedure of CO₂ copolymerization of propylene oxidecatalyzed by triethylborane was performed. Inside a glove box underargon, to a pre-dried 50 mL of autoclave fitted with magnetic stirringbar, 9.6 mg of potassium tert-butyloxide (86 μmol) was added followed bytriethylborane solution in THF (172 μmol) and propylene oxide (3 mL, 43mmol). CO₂ was charged into the sealed autoclave to 10 bar. Then,copolymerization was carried out under stirring at 60° C. After thereaction time for 16 hours, the carbon dioxide was slowly vented, andquenched the reaction with drops of 10% HCl. Dichloromathane was used toextract the polymer. The organic solution was concentrated and thepolymer was obtained after precipitation in cyclohexene or coldmethanol. The results were listed in Table 7. (see FIG. 51-54, 56).

EXAMPLE 18

A representative procedure of CO₂ copolymerization of cyclohexene oxidecatalyzed by triethylborane was performed. Inside a glove box underargon, to a pre-dried 50 mL of autoclave fitted with magnetic stirringbar, 45 mg of potassium tert-butyloxide (40 μmol) was added followed by3.0 mL of THF, triethylborane (80 umol), and 3.0 mL of cyclohexeneoxide. CO₂ was charged into the sealed autoclave to 10 bar. Then,copolymerization was carried out under vigorous stirring at 80° C. Afterthe reaction time, the carbon dioxide slowly vented, and the reactionquenched with drops of 10% HCl. Dichloromathane was used to dissolve anddilute the polymer. The polymer was obtained through precipitation incold methanol. The results were listed in Table 7, FIG. 55-56. FIGS.57A-57B a schematic diagram of preparing n-butyllithium/phosphazeneP₄-t-Bu superbase complex and H¹ NMR spectra for n-BuLi/P₄-t-Bu complex(400 MHz, benzene-d₆), according to one or more embodiments of thepresent disclosure.

The present invention is described with reference to the attachedfigures, wherein like reference numerals are used throughout the figuresto designate similar or equivalent elements. The figures are not drawnto scale and they are provided merely to illustrate the invention.Several aspects of the invention are described with reference to exampleapplications for illustration. It should be understood that numerousspecific details, relationships, and methods are set forth to provide anunderstanding of the invention. One skilled in the relevant art,however, will readily recognize that the invention can be practicedwithout one or more of the specific details or with other methods. Inother instances, well-known structures or operations are not shown indetail to avoid obscuring the invention. The present invention is notlimited by the illustrated ordering of acts or events, as some acts mayoccur in different orders and/or concurrently with other acts or events.Furthermore, not all illustrated acts or events are required toimplement a methodology in accordance with the present invention.

What is claimed is:
 1. A method of making a polycarbonate, comprising:contacting an epoxide monomer and carbon dioxide in the presence of anactivator and initiator to form a polycarbonate, wherein the activatoris a trialkyl borane, wherein the initiator includes an alcohol compoundand an organic cation, wherein the polycarbonate is formed undermetal-free conditions.
 2. The method of claim 1, wherein the epoxidemonomer is one or more of ethylene oxide, propylene oxide, 1-buteneoxide, 1-hexene oxide, 1-octene oxide, styrene oxide, cyclohexene oxide,allyl glycidyl ether, and butyl glycidyl ether.
 3. The method of claim1, wherein the activator is one or more of triethyl borane, trimethylborane, triisobutylborane, and triphenylborane.
 4. The method of claim1, wherein the alcohol compound includes more than one hydroxyl group.5. The method of claim 1, wherein the alcohol compound of the initiatoris one or more of 1,4-benzenedimethanol and benzyl alcohol.
 6. A methodof making a polycarbonate, comprising: contacting an epoxide monomer andcarbon dioxide in the presence of an activator and initiator to form apolycarbonate, wherein the activator is a trialkyl borane, wherein theinitiator includes an alcohol compound and an organic cation, whereinthe organic cation is a phosphazene base.
 7. The method of claim 1,wherein the initiator is one of the following: 1,4-benzenedimethanol andt-Bu-P₄; and benzyl alcohol and t-Bu-P₄.
 8. A method of making a blockcopolymer of polycarbonate, comprising: contacting a first epoxidemonomer and carbon dioxide in the presence of an activator includingtrialkyl borane and an initiator to form a first polycarbonate block,wherein the initiator includes an alcohol compound and an organiccation, and adding a second epoxide monomer to form a secondpolycarbonate block of a block copolymer that is different from thefirst polycarbonate block, wherein the block copolymer is formed undermetal-free conditions.
 9. The method of claim 8, wherein the firstepoxide monomer and the second epoxide monomer are different.
 10. Themethod of claim 8, wherein the first epoxide monomer and the secondepoxide monomer are one or more of ethylene oxide, propylene oxide,1-butene oxide, 1-hexene oxide, 1-octene oxide, styrene oxide,cyclohexene oxide, allyl glycidyl ether, and butyl glycidyl ether. 11.The method of claim 8, wherein the activator is one or more of triethylborane, trimethyl borane, triisobutylborane, and triphenylborane. 12.The method of claim 8, wherein the initiator includes an organic cationand either an alkali metal or alcohol compound.
 13. The method of claim8, wherein the organic cation is one or more of phosphazenium, ammonium,and phosphonium.
 14. The method of claim 8, wherein the alcohol compoundcontains more than one hydroxyl group.
 15. The method of claim 8,wherein the alcohol compound is one or more of a diol and triol.
 16. Themethod of claim 8, wherein the block copolymer is an ABA blockcopolymer, wherein A and B are different.